by jacob.andrew.parker:

What steps will reproduce the problem?

package main

import "net"
import "fmt"

func main () {
  ip := net.ParseIP ("123:")
  if ip == nil {
    fmt.Println ("sad")
  } else {
    fmt.Println ("yay")
  }
}

What is the expected output?
sad

What do you see instead?
panic: runtime error: index out of range

Which compiler are you using (5g, 6g, 8g, gccgo)?
6g

Which operating system are you using?
Ubuntu x64

Which revision are you using?  (hg identify)
0637076c39bc

Please provide any additional information below.