Integer Types in Go

Go offers several integer types because different values need different ranges. A signed type can hold negative and positive numbers. An unsigned type starts at zero, and the number of bits determines how high it can go. in The Golang Official Documentation

Type	Values or purpose
int8	−128 through 127
uint8	0 through 255
int16, int32, int64	Signed values with 16, 32, or 64 bits
uint16, uint32, uint64	Unsigned values with 16, 32, or 64 bits
int	Signed, either 32 or 64 bits
uint	Unsigned, with the same width as int

The table lists the common widths. With n bits, an unsigned type can store 0 through 2ⁿ − 1. A signed type uses part of its range for negative values, so it stores −2ⁿ⁻¹ through 2ⁿ⁻¹ − 1.

package main
 
import "fmt"
 
func main() {
	var signed int8 = -12
	var unsigned uint8 = 12
	fmt.Printf("%v %T\n", signed, signed)
	fmt.Printf("%v %T\n", unsigned, unsigned)
}

If you’ll run this, you’ll get

-12 int8
12 uint8

In the example, -12 fits in int8 but could not fit in uint8. The %T output confirms the two variables have different types. For ordinary counts and indices, int is usually convenient, choose a fixed-width type when the exact width is part of the data you are handling.