Contents

2. Variables

2. Variables

2.1 Variable Declaration

2.1.2 The Full Format

Syntax:

var variableList type

For example:

var age, height, weight int

2.2.2 Other Ways to Declare Variables:

  • Variables with initializers (if the initializers are present, type can be omitted and the variable will take the type of the initializers)

    Syntax:

    var variableList type = initializers
var variableList = initializers

    For example:

    var age, height, weight int = 18, 168, 56
var age, height, weight = 18, 168, 56

  • Inside the function, variables can be declared implicitly with shortcut := (This is not applicable for outside of function)

    Syntax:

    func function(){
  variableName := value
}

    For example:

    package main

import "fmt"

func main() {
  a := true
  fmt.Println(a)
}

2.3 Naming

2.3.1 Naming Criteria

The naming in Go must follow all the criteria [1]:

  1. A name must begin with a letter, and can have any number of additional letters and numbers.

  2. A function name cannot start with a number.

  3. A function name cannot contain spaces.

  4. If the functions/variables with names that start with an uppercase letter will be exported to other packages. If the function/variable name starts with a lowercase letter, it won’t be exported to other packages, but you can call this function/variable within the same package (exported means that function/variable can be called outside of the package). For example, Pi is an exported variable from package math, while pi is not. So, we can call Pi from math in our main program (sample code in file exported-names.go).

    import (
  "fmt"
  "math"
)

func main() {
    fmt.Println(math.Pi) // will work
    fmt.Println(math.pi) // will not work
}

  5. If a name consists of multiple words, each word after the first should be capitalized like this: empName, EmpAddress, etc.

  6. Function names are case-sensitive (go, Go and GO are three different variables).

2.3.2 Naming Convention

Besides rigid rules above, Go developers also develop their own culture for naming variables [2]

As a rule of thumb:

“The greater the distance between a name’s declaration and its uses, the longer the name should be.” – Andrew Gerrand

  • Name should use camel case (e.g., lastName) - and strictly avoid using underscore (e.g., ~~last_name~~)

  • Acronyms should be all capitalized (e.g., ServeHTTP)

  • Keep the name very short and concise. For common name such as index, it should be named i instead.

2.6 Reserved Keywords

There are 25 keywords in Go [3]

break        default      func         interface    select
case         defer        go           map          struct
chan         else         goto         package      switch
const        fallthrough  if           range        type
continue     for          import       return       var

and 37 reserved words

Constants:    true  false  iota  nil
Types:        int  int8  int16  int32  int64
			        uint  uint8  uint16  uint32  uint64  uintptr
			        float32  float64  complex128  complex64
			        bool  byte  rune  string  error
Functions:    make  len  cap  new  append  copy  close  delete
			        complex  real  imag
			        panic  recover

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