Update golang Docker tag to v1.26

.woodpecker.yml

@@ -1,6 +1,6 @@
 steps:
   test:
-    image: golang:1.25
+    image: golang:1.26
     commands:
       - go test ./...
   build:

Dockerfile

@@ -1,4 +1,4 @@
-FROM golang:1.25
+FROM golang:1.26
 WORKDIR /src
 COPY . ./
 RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build -v .