$ cat x.go
package main

import "os"

func main() {
    println(os.Getenv("TOOLONG"))
}

$ TOOLONG="too long too long too long too long too long too long too long too long
too long too long too long too long too long too long too long too long too long too
long too long too long too long too long too long too long too long too long too long
too long too long" go run x.go
[string too long]

Changing println to fmt.Println results in the string being printed.

The runtime cost of updating maxstring probably makes this not worth fixing.