The program available on The Go Playground reads
package main
import "fmt"
func main() {
var name string = nil
fmt.Println(name)
}
and yields an error
prog.go:6: cannot use nil as type string in assignment
I understand "" is the "zero value" for strings. I don't understand why I cannot assign nil to my string.
Because Golang string is a read-only slices of bytes.
However, a pointer to a string (*string) can be nil:
var s *string
s = nil
readonly := "readonly"
s = &readonly
dereference := *s
https://dhdersch.github.io/golang/2016/01/23/golang-when-to-use-string-pointers.html
Aedolon made some good points, but to go further, in other languages strings are convenient ways of representing arrays of bytes as characters. We need to do this a lot, so this specific use case of an array gets a lot of language support to make it easier to use. However, at the heart of the matter, you are working with an array, which is often able to be null in a language because it is a reference type. That is, the string isn't really null, the pointer to the array is null. Because many languages conflate these two things, programmers are used to having to check if a string is null before using it.
Go doesn't do this. A string cannot be nil, because the data structure in go doesn't allow it. You can have a pointer to a byte array holding character representations in go be null, but that isn't a string.