cgo **char to slice string

I have developed a pam module using the cgo. can not be converted to []string a ** char

func pam_sm_authenticate(pamh *C.pam_handle_t, flags C.int, argc C.int, argv **C.char) int { fmt.Println(C.GoString(*argv[0])) return 0 }

error is

invalid operation: argv[0] (type **C.char does not support indexing)

Please let me know if you know.