Windows - Process keeps running when stdin is set

The following works fine:
```go
func runPsCmd(psCmd string) {
pthPs := `C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe`

cmd := exec.Command(pthPs, "-Command", psCmd)

cmd.Stderr = os.Stderr
cmd.Stdout = os.Stdout
cmd.Stdin = os.Stdin

err := cmd.Start()
if err != nil {
panic(err)
}

err = cmd.Wait()
if err != nil {
exitError, ok := err.(*exec.ExitError)
if ok {
os.Exit(exitError.ExitCode())
} else {
panic(err)
}
}
os.Exit(0)
}

func main() {
runPsCmd("echo myTest")
}
```

However when doing the same but with:
```go
func runPsCmd(s ssh.Session, psCmd string) {
// [..]
cmd.Stderr = s
cmd.Stdout = s
cmd.Stdin = s
// [..]
}
```

`cmd.Wait()` blocks until I pressed Enter once. When I don't assign `cmd.Stdin` at all, it works as expected, but some programs may require user input. What could this by caused by? And how can this be fixed?