Generally, someone is good at doing something. On the other hand, someone is [simply] good in something. However, depending on which dialect you are speaking in, it depends. For instance, …
There's only one major case that leaps to mind where "good in" is idiomatically correct: He is good in bed. This can be generalized somewhat to "he is good in (location where certain …
There are some idiomatic expressions where “good in” is appropriate, but these are rather rare. The most common one is “to be good in bed”:
Anybody can be good in the country. 任何人在乡村都能变得善良. His this rank's substitution, may not be good in the transferring market's free man looks. 他这个级别的替补, 在转会市场的自由人中可 …
be good at 的意思是“擅长”，也可以用be good in ,后者一般用于美国英语中。例如：She is good at singing . 她歌唱得好。/ He is not only good in physics , but also good in other subjects . 他不 …
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