Table Of ContentTHE WAY TO GO
A Thorough Introduction to the Go Programming Language
IVO BALBAERT
The Way To Go
Also by Ivo Balbaert:
“Handboek Programmeren met Ruby en Rails.”, 2009, Van Duuren Media, ISBN:
978-90-5940-365-9
The Way To Go
a Thorough Introduction to the Go Programming Language
Ivo BaLBaerT
iUniverse, Inc.
Bloomington
The Way to Go
A Thorough Introduction to the Go Programming Language
Copyright © 2012 by Ivo Balbaert.
All rights reserved. No part of this book may be used or reproduced by any means, graphic, electronic, or mechanical,
including photocopying, recording, taping or by any information storage retrieval system without the written permission of
the publisher except in the case of brief quotations embodied in critical articles and reviews.
iUniverse books may be ordered through booksellers or by contacting:
iUniverse
1663 Liberty Drive
Bloomington, IN 47403
www.iuniverse.com
1-800-Authors (1-800-288-4677)
Because of the dynamic nature of the Internet, any web addresses or links contained in this book may have changed
since publication and may no longer be valid. The views expressed in this work are solely those of the author and do not
necessarily reflect the views of the publisher, and the publisher hereby disclaims any responsibility for them.
Any people depicted in stock imagery provided by Thinkstock are models, and such images are being used for illustrative
purposes only.
Certain stock imagery © Thinkstock.
ISBN: 978-1-4697-6916-5 (sc)
ISBN: 978-1-4697-6917-2 (ebk)
Printed in the United States of America
iUniverse rev. date: 03/05/2012
ConTenTs
Preface ................................................................................................................................xix
PART 1—WHY LEARN GO—GETTING STARTED
Chapter 1—Origins, Context and Popularity of Go ..............................................................1
1.1 Origins and evolution ...............................................................................................1
1.2 Main characteristics, context and reasons for developing a new language ...................4
1.2.1 Languages that influenced Go ........................................................................4
1.2.2 Why a new language? .....................................................................................5
1.2.3 Targets of the language ...................................................................................5
1.2.4 Guiding design principles ..............................................................................7
1.2.5 Characteristics of the language .......................................................................7
1.2.6 Uses of the language .......................................................................................8
1.2.7 Missing features? ............................................................................................9
1.2.8 Programming in Go .....................................................................................10
1.2.9 Summary .....................................................................................................10
Chapter 2—Installation and Runtime Environment ...........................................................11
2.1 Platforms and architectures ....................................................................................11
(1) The gc Go-compilers: .................................................................................11
(2) The gccgo-compiler: ...................................................................................13
(3) File extensions and packages: ......................................................................14
2.2 Go Environment variables .......................................................................................14
2.3 Installing Go on a Linux system ..............................................................................16
2.4 Installing Go on an OS X system ............................................................................21
2.5 Installing Go on a Windows system.........................................................................21
2.6 What is installed on your machine? ........................................................................26
2.7 The Go runtime ......................................................................................................27
2.8 A Go interpreter .....................................................................................................27
Chapter 3—Editors, IDE’s and Other tools.........................................................................28
3.1 Basic requirements for a decent Go development environment ................................28
3.2 Editors and Integrated Development Environments ................................................29
3.2.1. Golang LiteIDE .........................................................................................32
3.2.2. GoClipse .....................................................................................................33
3.3 Debuggers ...............................................................................................................34
3.4 Building and running go-programs with command- and Makefiles .........................35
3.5 Formatting code: go fmt or gofmt ...........................................................................39
3.6 Documenting code: go doc or godoc .......................................................................40
3.7 Other tools ..............................................................................................................41
3.8 Go’s performance ....................................................................................................41
3.9 Interaction with other languages. .............................................................................43
3.9.1. Interacting with C ......................................................................................43
3.9.2. Interacting with C++ ...................................................................................45
PART 2—CORE CONSTRUCTS AND TECHNIQUES OF THE LANGUAGE
Chapter 4—Basic constructs and elementary data types ......................................................49
4.1. Filenames—Keywords—Identifiers .........................................................................49
4.2. Basic structure and components of a Go-program ..................................................50
4.2.1 Packages, import and visibility .....................................................................51
4.2.3 Comments ...................................................................................................56
4.2.4 Types............................................................................................................57
4.2.5 General structure of a Go-program ..............................................................58
4.2.6 Conversions .................................................................................................60
4.2.7 About naming things in Go .........................................................................60
4.3. Constants ...............................................................................................................60
4.4. Variables .................................................................................................................63
4.4.1 Introduction ................................................................................................63
4.4.2 Value types and reference types ....................................................................66
4.4.3 Printing........................................................................................................68
4.4.4 Short form with the := assignment operator .................................................69
4.4.5 Init-functions ...............................................................................................70
4.5. Elementary types and operators ..............................................................................73
4.5.1. Boolean type bool .......................................................................................73
4.5.2. Numerical types ..........................................................................................75
4.5.2.1 ints and floats ............................................................................................75
4.5.2.2 Complex numbers ....................................................................................79
4.5.2.3 Bit operators .............................................................................................79
4.5.2.4 Logical operators .......................................................................................81
4.5.2.5 Arithmetic operators ................................................................................82
4.5.2.6 Random numbers .....................................................................................82
4.5.3. Operators and precedence ...........................................................................84
4.5.4. Aliasing types ..............................................................................................84
4.5.5. Character type ............................................................................................85
4.6. Strings ....................................................................................................................86
4.7. The strings and strconv package .............................................................................88
4.7.1—Prefixes and suffixes: ..................................................................................88
4.7.2—Testing whether a string contains a substring: ............................................89
4.7.3—Indicating at which position (index) a substring or character occurs
in a string: ..................................................................................................89
4.7.4—Replacing a substring: ...............................................................................90
4.7.5—Counting occurrences of a substring: .........................................................90
4.7.6—Repeating a string:.....................................................................................90
4.7.7—Changing the case of a string:....................................................................91
4.7.8—Trimming a string: ....................................................................................92
4.7.9—Splitting a string: .......................................................................................92
4.7.10—Joining over a slice: .................................................................................92
4.7.11—Reading from a string: .............................................................................93
4.8. Times and dates ......................................................................................................95
4.9. Pointers ..................................................................................................................96
Chapter 5—Control structures ..........................................................................................101
5.1—The if else construct ...........................................................................................101
5.2—Testing for errors on functions with multiple return values .................................106
5.3—The switch keyword ...........................................................................................110
5.4—The for construct ...............................................................................................114
5.4.1 Counter-controlled iteration ......................................................................114
Character on position 2 is: ..........................................................................................116
5.4.2 Condition-controlled iteration ..................................................................117
5.4.3 Infinite loops ............................................................................................118
5.4.4 The for range construct ..............................................................................119
5.5—Break / continue .................................................................................................121
5.6—Use of labels with break and continue—goto ......................................................123
Chapter 6—Functions.......................................................................................................126
6.1 Introduction ..........................................................................................................126
6.2 Parameters and return values .................................................................................129
6.2.1 Call by value / Call by reference .................................................................129
6.2.2 Named return variables ..............................................................................131
6.2.3 Blank identifier ..........................................................................................133
6.2.4 Changing an outside variable .....................................................................134
6.3 Passing a variable number of parameters ................................................................135
6.4 Defer and tracing ..................................................................................................137
6.5 Built-in functions ..................................................................................................142
6.6 Recursive functions ...............................................................................................143
6.8 Closures (function literals) ....................................................................................147
6.9 Applying closures: a function returning another function .....................................150
6.10 Debugging with closures .....................................................................................153
6.11 Timing a function ..............................................................................................154
6.12 Using memoization for performance ...................................................................154
Chapter 7—Arrays and Slices ............................................................................................157
7.1 Declaration and initialization ................................................................................157
7.1.1 Concept .....................................................................................................157
7.1.2 Array literals ...............................................................................................161
7.1.3 Multidimensional arrays .............................................................................162
7.1.4 Passing an array to a function .....................................................................163
7.2 Slices .....................................................................................................................164
7.2.1 Concept .....................................................................................................164
7.2.2 Passing a slice to a function ........................................................................168
7.2.3 Creating a slice with make() .......................................................................168
7.2.4 Difference between new() and make() ........................................................170
7.2.5 Multidimensional slices ..............................................................................171
7.2.6 The bytes package ......................................................................................171
7.3 For range construct ...............................................................................................172
7.4 Reslicing ................................................................................................................175
7.5 Copying and appending slices ...............................................................................176
7.6 Applying strings, arrays and slices ..........................................................................178
7.6.1 Making a slice of bytes from a string ..........................................................178
7.6.2 Making a substring of a string ....................................................................179
7.6.3 Memory representation of a string and a slice .............................................179
7.6.4 Changing a character in a string .................................................................180
7.6.5 Comparison function for byte arrays ..........................................................180
7.6.6 Searching and sorting slices and arrays ......................................................181
7.6.7 Simulating operations with append ............................................................182
7.6.8 Slices and garbage collection ......................................................................182
Chapter 8—Maps .............................................................................................................185
8.1 Declaration, initialization and make ......................................................................185
8.1.1 Concept .....................................................................................................185
8.1.2 Map capacity .............................................................................................188
8.1.3 Slices as map values ....................................................................................188
8.2 Testing if a key-value item exists in a map—Deleting an element ..........................188
8.3 The for range construct .........................................................................................190
8.4 A slice of maps .....................................................................................................191
8.5 Sorting a map ........................................................................................................192
8.6 Inverting a map .....................................................................................................194
Chapter 9—Packages ........................................................................................................196
A The standard library .................................................................................................196
9.1 Overview of the standard library. ...........................................................................196
9.2 The regexp package. ..............................................................................................199
9.3 Locking and the sync package. ..............................................................................200
9.4 Accurate computations and the big package. .........................................................202
B Custom and external packages: use, build, test, document, install ............................203
9.5 Custom packages and visibility ..............................................................................203
9.6 Using godoc for your custom packages. .................................................................208
9.7 Using go install for installing custom packages. .....................................................210
9.8 Custom packages: map structure, go install and go test .........................................212
9.8.1 Map-structure for custom packages ............................................................212
9.8.2 Locally installing the package .....................................................................215
9.8.3 OS dependent code ....................................................................................216
9.9 Using git for distribution and installation. .............................................................216
9.9.1 Installing to github ....................................................................................216
9.9.2 Installing from github ................................................................................217
9.10 Go external packages and projects. .....................................................................218
9.11 Using an external library in a Go program. ..........................................................219
Chapter 10—Structs and Methods ....................................................................................224
10.1 Definition of a struct ...........................................................................................224
10.2 Creating a struct variable with a Factory method .................................................232
10.2.1 A factory for structs..................................................................................232
10.2.2 new() and make() revisited for maps and structs: ......................................234
10.3 Custom package using structs ..............................................................................235
10.4 Structs with tags ..................................................................................................236
10.5 Anonymous fields and embedded structs .............................................................237
10.5.1 Definition ................................................................................................237
