在Golang的MacOSx上执行命令

I have a simple golang program to start an application in MacOSx.

package main

import (
    "io"
    "log"
    "os/exec"
)
func main() {
out1,err1 := exec.Command("/usr/bin/open ", " -a", "calcultor").Output()
log.Printf(" output is err  ", err1)
log.Printf(" output is err  ", out1)

}

I expect it to start application in calculator after execution but i receive following errors

2017/04/26 16:01:26 output is err%!(EXTRA *os.PathError=fork/exec /usr/bin/open : no such file or directory) 2017/04/26 16:01:26 output is out%!(EXTRA []uint8=[])

I am trying it on OSx 10.11.

There's a spelling mistake - "calcultor" should be "calculator".