[utils] add a function to ask user for passphrase

Signed-off-by: Leo Chen <leo@harmony.one>

internal/utils/passphrase.go

@@ -0,0 +1,21 @@
+package utils
+
+import (
+	"fmt"
+	"syscall"
+
+	"golang.org/x/crypto/ssh/terminal"
+)
+
+// AskForPassphrase return passphrase using password input
+func AskForPassphrase(prompt string) string {
+	fmt.Printf(prompt)
+	bytePassword, err := terminal.ReadPassword(int(syscall.Stdin))
+	if err != nil {
+		panic("read password error")
+	}
+	password := string(bytePassword)
+	fmt.Println()
+
+	return password
+}