when the letter reaches you,I am going to arrive in Hong kon

你自己翻译一边,没有歧义么?
I am going to arrive in HK------ 这个明显错了,arrive能用be going to搭配吗?打算到达?要么是I'm going to go to HK要不就是I will have been in HK.
两种写法但意思有差异：
1.I am going to go to HK after the letter reaches you.
2.I will have been in HK when the letter reaches you.