use drone-ci instead of gitlab-ci and add release

.drone.yml

@@ -0,0 +1,24 @@
+---
+kind: pipeline
+name: default
+
+steps:
+- name: golang
+  image: golang
+  commands:
+    - go vet
+    - go build
+    - go test
+
+- name: gitea_release
+  image: plugins/gitea-release
+  settings:
+    base_url: https://git.preisner.eu
+    api_key:
+      from_secret: gitea_api
+    files:
+      - dyndns-server
+    checksum:
+      - sha256
+  when:
+    event: tag