style: format code with Go fmt and Gofumpt

This commit fixes the style issues introduced in efb379c according to the output
from Go fmt and Gofumpt.

Details: #1

lura/proxy.go

@@ -18,8 +18,8 @@ import (
 )
 
 func middlewareProxy(next proxy.Proxy, tracer trace.Tracer, urlPattern string, duration metric.Float64Histogram,
-	tAttrs []attribute.KeyValue, mAttrs metric.MeasurementOption) func(ctx context.Context, req *proxy.Request) (*proxy.Response, error) {
-
+	tAttrs []attribute.KeyValue, mAttrs metric.MeasurementOption,
+) func(ctx context.Context, req *proxy.Request) (*proxy.Response, error) {
 	return func(ctx context.Context, req *proxy.Request) (*proxy.Response, error) {
 		var span trace.Span
 		if tracer != nil {
@@ -70,7 +70,6 @@ func middlewareProxy(next proxy.Proxy, tracer trace.Tracer, urlPattern string, d
 func Middleware(gsf state.GetterFn, metricsEnabled bool, tracesEnabled bool,
 	stageName string, urlPattern string, staticAttrs []attribute.KeyValue,
 ) proxy.Middleware {
-
 	mAttrs := make([]attribute.KeyValue, 0, len(staticAttrs)+1)
 	tAttrs := make([]attribute.KeyValue, 0, len(staticAttrs)+1)