CreateLambdaContextLocally.go

func CreateLambdaContextLocally(next http.Handler) http.Handler {

	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		type MyCustomClaims struct {
			Username string `json:"cognito:username"`
			Email           string `json:"email"`
			// custom claims etc
			jwt.StandardClaims
		}

		tokenString := r.Header.Get("Authorization")
		// if we want to properly pass token must use jwt to parse
		token, err := jwt.ParseWithClaims(tokenString, &MyCustomClaims{}, func(token *jwt.Token) (interface{}, error) {
      set, err := jwk.Fetch("https://cognito-idp.{region}.amazonaws.com/{cognito-id}/.well-known/jwks.json")
			// error handling & set key

			return key, err
		})
		if err != nil {
			// error
		}

		// create some new claims
		var claims *MyCustomClaims
		claims = token.Claims.(*MyCustomClaims)

		// Create that new APIGateWayProxyRequest and smack it on the request
		test := events.APIGatewayProxyRequest{
			RequestContext: events.APIGatewayProxyRequestContext{
				Authorizer: map[string]interface{}{"claims": claims},
			}}

		// create new context - must be able to fetch correct proxy request key
		ctx := context.WithValue(r.Context(), GetProxyRequestKey(), test)
		r = r.Clone(ctx)

		// We pass r onto the next function
		next.ServeHTTP(w, r)
	})
}