How to execute a simple Windows command in Golang?

I got the same error as you.
But dystroy is correct: You can’t run del or any other command built into cmd because there is no del.exe file (or any other del-executable for that matter).

I got it to work with:

package main
    
import(
    "fmt"
    "os/exec"
)
    
func main() {
    var c *exec.Cmd

    switch runtime.GOOS{
    case "windows":
        c = exec.Command("cmd", "/C", "del", "D:\\a.txt")

    default://Mac & Linux
        c = exec.Command("rm", "-f", "/d/a.txt")
    }

    if err := c.Run(); err != nil { 
        fmt.Println("Error: ", err)
    }
}