go c 数据类型映射

C.char
C.schar (signed char)
C.uchar (unsigned char)
C.short
C.ushort (unsigned short)
C.int
C.uint (unsigned int)
C.long
C.ulong (unsigned long)
C.longlong (long long)
C.ulonglong (unsigned long long)
C.float
C.double. 


unsafe.Pointer (void*)

// Go string to C string
func C.CString(string) *C.char

var val []byte
(*C.char)(unsafe.Pointer(&val[0]))