Revert "Fix broken build due to kin backwards-incompatible change (#322)"

This reverts commit 88f937a7166a1e3603e3ec96e57e45af7a998373.

The kin legacy routers force pulling in kin-openapi@0.52.0 which requires
Go 1.16

Author: mromaszewicz

oapi_validate.go

@@ -23,8 +23,6 @@ import (
 
 	"github.com/getkin/kin-openapi/openapi3"
 	"github.com/getkin/kin-openapi/openapi3filter"
-	"github.com/getkin/kin-openapi/routers"
-	"github.com/getkin/kin-openapi/routers/legacy"
 	"github.com/labstack/echo/v4"
 	echomiddleware "github.com/labstack/echo/v4/middleware"
 )
@@ -67,11 +65,7 @@ type Options struct {
 
 // Create a validator from a swagger object, with validation options
 func OapiRequestValidatorWithOptions(swagger *openapi3.Swagger, options *Options) echo.MiddlewareFunc {
-	router, err := legacy.NewRouter(swagger)
-	if err != nil {
-		panic(err)
-	}
-
+	router := openapi3filter.NewRouter().WithSwagger(swagger)
 	skipper := getSkipperFromOptions(options)
 	return func(next echo.HandlerFunc) echo.HandlerFunc {
 		return func(c echo.Context) error {
@@ -90,14 +84,14 @@ func OapiRequestValidatorWithOptions(swagger *openapi3.Swagger, options *Options
 
 // This function is called from the middleware above and actually does the work
 // of validating a request.
-func ValidateRequestFromContext(ctx echo.Context, router routers.Router, options *Options) error {
+func ValidateRequestFromContext(ctx echo.Context, router *openapi3filter.Router, options *Options) error {
 	req := ctx.Request()
-	route, pathParams, err := router.FindRoute(req)
+	route, pathParams, err := router.FindRoute(req.Method, req.URL)
 
 	// We failed to find a matching route for the request.
 	if err != nil {
 		switch e := err.(type) {
-		case *routers.RouteError:
+		case *openapi3filter.RouteError:
 			// We've got a bad request, the path requested doesn't match
 			// either server, or path, or something.
 			return echo.NewHTTPError(http.StatusBadRequest, e.Reason)