add custom context support

[mei-rune]

add custom context support

Originally posted by @runner-mei in #1302 (comment)

[StevenACoffman]

Not sure this is the same, but my use case is that I would like to combine echo and gqlgen. There is a gqlgen gin recipe where you create a gin middleware to add the gin.Context to the context.Context.
Ref: https://gqlgen.com/recipes/gin/#accessing-gin-context

[mei-rune]

@StevenACoffman yes, similar.

[StevenACoffman]

Original comment quoted below:

I like it Context as interface, but need improve now code.

add methods:

(e *Echo) SetNewContext(newCtx  func() Context) {
 e.pool.New = func() interface{} {
		return newCtx()
	}
}

func (e *Echo) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	c := e.pool.Get().(Context)
	c.Reset(r, w)
	......
	c.Free()
	e.pool.Put(c)
}

my client code:

type MyContext strcut {
	echo.Context
	
	MyField1 xxx
	MyField2 xxx
	MyField3 xxx
	.... xxx
}

func (ctx *MyContext) Free() {
   ctx.MyField1 = nil
   ctx.MyField2 = nil
   ctx.MyField3 = nil
   ....
}

func toEchoFunc(h func(ctx *MyContext) error) echo.HandlerFunc {
	return func(ctx echo.Context) error {
		return h(ctx.(*MyContext))
	}
}

echo.SetNew(func() echo.Context {
	return &MyContext{Context: echo.NewContext()}
})

echo.GET("/xxx", toEchoFunc(func(ctx *MyContext) error {
   xxxxxxx
}))

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[StevenACoffman]

By the way, I got things working here: https://github.com/StevenACoffman/echogqlgen