Golang Data Types

Basic data types

int  int8  int16  int32  int64
uint uint8 uint16 uint32 uint64 uintptr
byte // same as for uint8
rune // represents a Unicode code point
float32 float64
complex64 complex128


Strings are made up of “runes” rather than chars. Rather than having char and wchar for characters and unicode characters, a rune is a “code point” as defined in the Unicode standard. Internally it is  a 32-bit representation.

nihao := "你好"
for index, runeValue := range nihao {
 fmt.Printf("Character %#U Byte position %d\n", runeValue, index)

String to array of runes

runes := []rune(s)

rune array to string

str := string(runes)


A slice consists of a pointer to an array segment, length of the segment and its capacity i.e. the maximum length of the segment.

  • Create
b = make([]T, len(a))
  • Add element
var s []int
s = append(s, 1) //add one element 
s = append(s, 2,3,4) //add multiple
s = append(s, s1…) // append another slice
  • Delete
s[len(s)-1] //remove last element
  • Iterate
for index, value := range s {

  • Two dimensional slices

Slices are one-dimensional. We have to compose it to form two-dimensional arrays.

matrix := make([][]int, row) 
for m := range matrix { 
     matrix[m] = make([]int, col)

When you pass a slice to a function, since it is a pointer to an array you just get a copy of the slice structure. It will still point to the same underlying array segment.


The built-in map type implements a hash table. Map is also a reference type like slices. Maps, like channels, but unlike slices, are just pointers to runtime types. As you saw above, a map is just a pointer to a runtime.hmap structure. So when we declare a map using var, its value will be nil until initialized using make. Attempts to access a nil map will result in a panic.

  • Create
x := make(map[int]int)
  • Add element
x[1] = 10
  • Delete element
delete(x, 1)
  • Find value
val, ok := x[key]
  • Iterating
for key, val:= range x { 
   println("Key:", key, "Value:", val ,"Value:", m[k]) 
  • Size

All operations on a map are in constant time.


struct is a collection of fields.

A struct can have methods defined on it. There are two kinds of methods that can be defined on a  struct, a value receiver and a pointer receiver.

type T struct {
	a int
func (tv  T) Mv(a int) int         { return 0 }  // value receiver
func (tp *T) Mp(f float32) float32 { return 1 }  // pointer receiver

It all comes down which one is better for the problem at hand.

Pass by value or reference


There are boolean constantsrune constantsinteger constantsfloating-point constantscomplex constants, and string constants. Rune, integer, floating-point, and complex constants are collectively called numeric constants.

A constant expression may contain only constant operands and are evaluated at compile time. As such, there is no such thing as array constant in Go. Slices and arrays are always evaluated during runtime. They can only be defined as variables.

Interesting Reads:



Leave a Reply

Please log in using one of these methods to post your comment:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s