echo/website/content/guide/context.md

+++ title = "Context" description = "Context in Echo" [menu.side] name = "Context" identifier = "context" parent = "guide" weight = 5 +++

Context

echo.Context represents the context of the current HTTP request. It holds request and response reference, path, path parameters, data, registered handler and APIs to read request and write response. Context is 100% compatible with standard context.Context. As Context is an interface, it is easy to extend it with custom APIs.

Extending Context

Define a custom context

type CustomContext struct {
	echo.Context
}

func (c *CustomContext) Foo() {
	println("foo")
}

func (c *CustomContext) Bar() {
	println("bar")
}

Create a middleware to extend default context

e.Use(func(h echo.HandlerFunc) echo.HandlerFunc {
	return func(c echo.Context) error {
		cc := &CustomContext{c}
		return h(cc)
	}
})

This middleware should be registered before any other middleware.

Use in handler

e.GET("/", func(c echo.Context) error {
	cc := c.(*CustomContext)
	cc.Foo()
	cc.Bar()
	return cc.String(200, "OK")
})

Standard Context

echo.Context embeds standard context.Context interface, so all it's functions are available right from echo.Context.

Example

e.GET("/users/:name", func(c echo.Context) error) {
    c.SetContext(context.WithValue(nil, "key", "val"))
    // Pass it down...
    // Use it...
    val := c.Value("key").(string)
    return c.String(http.StatusOK, name)
})