style: format code with Go fmt and Gofumpt

This commit fixes the style issues introduced in 52885ad according to the output
from Go fmt and Gofumpt.

Details: #1

lura/backend.go

@@ -14,24 +14,22 @@ import (
 	clienthttp "github.com/krakend/krakend-otel/http/client"
 )
 
-var (
-	defaultOpts = otelconfig.BackendOpts{
-		Metrics: &otelconfig.BackendMetricOpts{
-			DisableStage:       false,
-			RoundTrip:          true,
-			ReadPayload:        true,
-			DetailedConnection: true,
-			StaticAttributes:   make(map[string]string),
-		},
-		Traces: &otelconfig.BackendTraceOpts{
-			DisableStage:       false,
-			RoundTrip:          true,
-			ReadPayload:        true,
-			DetailedConnection: true,
-			StaticAttributes:   make(map[string]string),
-		},
-	}
-)
+var defaultOpts = otelconfig.BackendOpts{
+	Metrics: &otelconfig.BackendMetricOpts{
+		DisableStage:       false,
+		RoundTrip:          true,
+		ReadPayload:        true,
+		DetailedConnection: true,
+		StaticAttributes:   make(map[string]string),
+	},
+	Traces: &otelconfig.BackendTraceOpts{
+		DisableStage:       false,
+		RoundTrip:          true,
+		ReadPayload:        true,
+		DetailedConnection: true,
+		StaticAttributes:   make(map[string]string),
+	},
+}
 
 // HTTPRequestExecutorFromConfig creates an HTTPRequestExecutor to be used
 // for the backend requests.

router/gin/endpoint.go

@@ -17,14 +17,12 @@ import (
 	"github.com/krakend/krakend-otel/state"
 )
 
-var (
-	defaultSkipPaths = []string{
-		"/healthz",
-		"/_ah/health",
-		"/__debug",
-		"/__echo",
-	}
-)
+var defaultSkipPaths = []string{
+	"/healthz",
+	"/_ah/health",
+	"/__debug",
+	"/__echo",
+}
 
 // defaultRouterOpts return the default options when no options
 // are provided

router/gin/propagation.go

@@ -11,8 +11,8 @@ import (
 )
 
 func PropagationMiddleware(next gin.HandlerFunc,
-	prop propagation.TextMapPropagator) gin.HandlerFunc {
-
+	prop propagation.TextMapPropagator,
+) gin.HandlerFunc {
 	if prop == nil {
 		return next
 	}