gin.Context should use sync.Map

[ajackson-cpi]

I'm seeing a "concurrent map" crash where a gin.Context.Copy() product in another goroutine is modifying a key while it's being read elsewhere. context.Context (which is the interface being implemented) will not have a problem with this.

[thinkerou]

but sync.Map in go1.9 and go1.9+

[himyxia]

are there any circumstances that context.Copy() are called by multiple concurrency goroutines ?

[artong0416]

I have the same problem, is there any good solutions?

[thinkerou]

please see ref #700 #1317 #1335