Convert string array to byte array in go

Given an string array which only contains single characters such as:

ex := [...]string{"a","o",".",".","2",".",".","9"}

is there a way to get a byte array with same content but with bytes instead of strings?

Use a conversion to convert each string to a []byte.

ex := [...]string{"a", "o", ".", ".", "2", ".", ".", "9"}
var ey [len(ex)][]byte
for i := range ex {
	ey[i] = []byte(ex[i])
}

Use this code if your intent is to get a byte array of the joined strings. This code only works when the strings are single ASCII characters.

ex := [...]string{"a", "o", ".", ".", "2", ".", ".", "9"}
var ey [len(ex)]byte
for i := range ex {
	ey[i] = ex[i][0]
}

Use this expression of you want to get a slice of bytes of the joined strings: []byte(strings.Join(ex[:], ""))

I don't know the your context for doing this, but my guess is that it's more appropriate to use a slice than an array:

ex := []string{"a", "o", ".", ".", "2", ".", ".", "9"}
ey := make([][]byte, len(ex))
for i := range ex {
	ey[i] = []byte(ex[i])
}

..

s := []byte(strings.Join(ex, ""))

This seems to do it:

package main

import (
   "fmt"
   "strings"
)

func main() {
   a := [...]string{"a","o",".",".","2",".",".","9"}
   var b [len(a)]byte
   c := strings.Join(a[:], "")
   copy(b[:], c)
   // [8]uint8{0x61, 0x6f, 0x2e, 0x2e, 0x32, 0x2e, 0x2e, 0x39}
   fmt.Printf("%#v\n", b)
}

https://godocs.io/strings#Join

Depending on if this is part of a code-generation pipeline, you can do this a couple of ways.

Directly:

bs := [...]byte{'a', 'o', '.', '.', '2', '.', '.', '9'}

or indirectly:

ex := [...]string{"a", "o", ".", ".", "2", ".", ".", "9"}

bs := [...]byte{
	ex[0][0],
	ex[1][0],
	ex[2][0],
	ex[3][0],
	ex[4][0],
	ex[5][0],
	ex[6][0],
	ex[7][0],
} // type [8]int8  i.e. [8]byte

https://play.golang.org/p/iMEjFpCKAaW

Depending on your use case, these ways may be too rigid. For dynamic initialization methods see the other answers here.