Add echo support

[watermelo]

Issue #35

Adding support for Echo

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[watermelo]

Hi @sapessi , I have modified it. 😄

[sapessi]

Thanks @watermelo! Merging.

[harrisonhjones]

I'm not super familiar with how go modules works but does this commit add another dependency to the list of required dependencies to build this package? If so isn't this something we should actively avoid? If I don't use echo in my project but I do use this package why should I have to depend on echo?

The adapter, while cool and useful, should probably live in some example folder/project in my opinion.

[sapessi]

I assumed Go was not going to build/package dependencies that are not used in your application. Regardless, you make a good point @harrisonhjones, I will change this to have multiple modules so that each adapter is its own mod with dependencies.

[harrisonhjones]

More testing might be worth it but I just threw together a quick project:

main.go

package main

import "path/to/dummy"

func main() {
    dummy.Bar()
}

dummy/foo.go

package dummy_dep

func Bar() int {
    return 0
}

dummy/baz.go

package dummy_dep

import "corge" // Not a real package

func Qux() int {
    corge.Bark()
}

And then when I try to go run main.go I get:

cannot find package "corge" in any of:
    C:\Go\src\corge (from $GOROOT)
    C:\Users\hhjones\go\src\corge (from $GOPATH)

So, unfortunately, it looks like Go does try to find all dependencies during compilation.