Extracting substrings in Go

Go strings are not null terminated, and to remove the last char of a string you can simply do:

s = s[:len(s)-1]

This is the simple one to perform substring in Go

package main

import "fmt"

var p = fmt.Println

func main() {

  value := "address;bar"

  // Take substring from index 2 to length of string
  substring := value[2:len(value)]
  p(substring)

}

WARNING: operating on strings alone will only work with ASCII and will count wrong when input is a non-ASCII UTF-8 encoded character, and will probably even corrupt characters since it cuts multibyte chars mid-sequence.

Here's a UTF-8-aware version:

// NOTE: this isn't multi-Unicode-codepoint aware, like specifying skintone or
//       gender of an emoji: https://unicode.org/emoji/charts/full-emoji-modifiers.html
func substr(input string, start int, length int) string {
    asRunes := []rune(input)
    
    if start >= len(asRunes) {
        return ""
    }
    
    if start+length > len(asRunes) {
        length = len(asRunes) - start
    }
    
    return string(asRunes[start : start+length])
}

It looks like you're confused by the working of slices and the string storage format, which is different from what you have in C.

• any slice in Go stores the length (in bytes), so you don't have to care about the cost of the len operation : there is no need to count
• Go strings aren't null terminated, so you don't have to remove a null byte, and you don't have to add 1 after slicing by adding an empty string.

To remove the last char (if it's a one byte char), simply do

inputFmt:=input[:len(input)-1]