refactor: enhance Docker CLI installation and build process in publish-image workflow

.dockerignore

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+.git
+.gitea
+.env
+*.log

.env.example

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+# Discord Bot Token
+# Zu finden unter https://discord.com/developers/applications → Bot → Token
+DISCORD_TOKEN=dein_token_hier
+TARGET_CHANNEL_NAME=mein-channel

.gitea/workflows/build.yml

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+name: Build
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+
+jobs:
+  build:
+    runs-on: docker
+    container:
+      image: node:20
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Set up Go
+        uses: actions/setup-go@v5
+        with:
+          go-version-file: go.mod
+          cache: false
+
+      - name: Build
+        run: go build ./...

.gitea/workflows/publish-image.yml

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+name: Publish Docker Image
+
+on:
+  push:
+    branches:
+      - main
+    tags:
+      - "v*"
+  workflow_dispatch:
+
+jobs:
+  docker:
+    runs-on: docker
+    container:
+      image: node:20-alpine
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Install Docker CLI + Buildx
+        shell: sh
+        run: |
+          apk add --no-cache docker-cli docker-cli-buildx
+
+      - name: Build image metadata
+        id: meta
+        shell: sh
+        run: |
+          SERVER_URL="${GITHUB_SERVER_URL:-${GITEA_SERVER_URL:-}}"
+          if [ -z "$SERVER_URL" ]; then
+            echo "Neither GITHUB_SERVER_URL nor GITEA_SERVER_URL is set."
+            exit 1
+          fi
+
+          REGISTRY_HOST="${SERVER_URL#http://}"
+          REGISTRY_HOST="${REGISTRY_HOST#https://}"
+          IMAGE_REPO="$(echo "$GITHUB_REPOSITORY" | tr '[:upper:]' '[:lower:]')"
+
+          echo "registry_host=$REGISTRY_HOST" >> "$GITHUB_OUTPUT"
+          echo "image=$REGISTRY_HOST/$IMAGE_REPO" >> "$GITHUB_OUTPUT"
+
+      - name: Log in to Gitea Container Registry
+        shell: sh
+        env:
+          REGISTRY_USERNAME: ${{ secrets.REGISTRY_USERNAME }}
+          REGISTRY_TOKEN: ${{ secrets.REGISTRY_TOKEN }}
+          LEGACY_TOKEN: ${{ secrets.GITEA_TOKEN }}
+          ACTOR_USERNAME: ${{ github.actor }}
+        run: |
+          USERNAME="$REGISTRY_USERNAME"
+          TOKEN="$REGISTRY_TOKEN"
+
+          if [ -z "$USERNAME" ]; then
+            USERNAME="$ACTOR_USERNAME"
+          fi
+
+          if [ -z "$TOKEN" ]; then
+            TOKEN="$LEGACY_TOKEN"
+          fi
+
+          if [ -z "$USERNAME" ] || [ -z "$TOKEN" ]; then
+            echo "Registry login failed: set REGISTRY_USERNAME and REGISTRY_TOKEN (or fallback GITEA_TOKEN)."
+            exit 1
+          fi
+
+          echo "$TOKEN" | docker login "${{ steps.meta.outputs.registry_host }}" -u "$USERNAME" --password-stdin
+
+      - name: Build and push image
+        shell: sh
+        run: |
+          IMAGE="${{ steps.meta.outputs.image }}"
+          SHA_TAG="${GITHUB_SHA}"
+          REF_TYPE="${GITHUB_REF_TYPE}"
+          REF_NAME="${GITHUB_REF_NAME}"
+
+          TAG_ARGS="--tag $IMAGE:$SHA_TAG"
+
+          # latest only for pushes to main
+          if [ "$REF_TYPE" = "branch" ] && [ "$REF_NAME" = "main" ]; then
+            TAG_ARGS="$TAG_ARGS --tag $IMAGE:latest"
+          fi
+
+          # semver tags for refs like v1.2.3 -> v1.2.3, v1.2, v1
+          if [ "$REF_TYPE" = "tag" ]; then
+            case "$REF_NAME" in
+              v[0-9]*.[0-9]*.[0-9]*)
+                MAJOR="$(echo "$REF_NAME" | cut -d. -f1)"
+                MINOR="$(echo "$REF_NAME" | cut -d. -f2)"
+                TAG_ARGS="$TAG_ARGS --tag $IMAGE:$REF_NAME --tag $IMAGE:$MAJOR.$MINOR --tag $IMAGE:$MAJOR"
+                ;;
+              *)
+                TAG_ARGS="$TAG_ARGS --tag $IMAGE:$REF_NAME"
+                ;;
+            esac
+          fi
+
+          docker buildx version
+          docker buildx build --push $TAG_ARGS .

Dockerfile

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+FROM golang:1.23-alpine AS builder
+
+WORKDIR /src
+
+COPY go.mod go.sum ./
+RUN go mod download
+
+COPY . .
+RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build -trimpath -ldflags="-s -w" -o /out/discord-thread-bot .
+
+FROM gcr.io/distroless/static-debian12:nonroot
+
+WORKDIR /app
+COPY --from=builder /out/discord-thread-bot /app/discord-thread-bot
+
+ENTRYPOINT ["/app/discord-thread-bot"]

go.mod

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+module discord-thread-bot
+
+go 1.23.0
+
+require github.com/bwmarrin/discordgo v0.29.0
+
+require (
+	github.com/gorilla/websocket v1.5.3 // indirect
+	github.com/joho/godotenv v1.5.1 // indirect
+	golang.org/x/crypto v0.38.0 // indirect
+	golang.org/x/sys v0.33.0 // indirect
+)

go.sum

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+github.com/bwmarrin/discordgo v0.29.0 h1:FmWeXFaKUwrcL3Cx65c20bTRW+vOb6k8AnaP+EgjDno=
+github.com/bwmarrin/discordgo v0.29.0/go.mod h1:NJZpH+1AfhIcyQsPeuBKsUtYrRnjkyu0kIVMCHkZtRY=
+github.com/gorilla/websocket v1.4.2/go.mod h1:YR8l580nyteQvAITg2hZ9XVh4b55+EU/adAjf1fMHhE=
+github.com/gorilla/websocket v1.5.3 h1:saDtZ6Pbx/0u+bgYQ3q96pZgCzfhKXGPqt7kZ72aNNg=
+github.com/gorilla/websocket v1.5.3/go.mod h1:YR8l580nyteQvAITg2hZ9XVh4b55+EU/adAjf1fMHhE=
+github.com/joho/godotenv v1.5.1 h1:7eLL/+HRGLY0ldzfGMeQkb7vMd0as4CfYvUVzLqw0N0=
+github.com/joho/godotenv v1.5.1/go.mod h1:f4LDr5Voq0i2e/R5DDNOoa2zzDfwtkZa6DnEwAbqwq4=
+golang.org/x/crypto v0.0.0-20210421170649-83a5a9bb288b/go.mod h1:T9bdIzuCu7OtxOm1hfPfRQxPLYneinmdGuTeoZ9dtd4=
+golang.org/x/crypto v0.38.0 h1:jt+WWG8IZlBnVbomuhg2Mdq0+BBQaHbtqHEFEigjUV8=
+golang.org/x/crypto v0.38.0/go.mod h1:MvrbAqul58NNYPKnOra203SB9vpuZW0e+RRZV+Ggqjw=
+golang.org/x/net v0.0.0-20210226172049-e18ecbb05110/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
+golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.33.0 h1:q3i8TbbEz+JRD9ywIRlyRAQbM0qF7hu24q3teo2hbuw=
+golang.org/x/sys v0.33.0/go.mod h1:BJP2sWEmIv4KK5OTEluFJCKSidICx8ciO85XgH3Ak8k=
+golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
+golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
+golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=

main.go

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+package main
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"os/signal"
+	"syscall"
+
+	"github.com/bwmarrin/discordgo"
+	"github.com/joho/godotenv"
+)
+
+func main() {
+	if err := godotenv.Load(); err != nil && !os.IsNotExist(err) {
+		log.Println("Warnung: .env-Datei konnte nicht geladen werden:", err)
+	}
+
+	token := os.Getenv("DISCORD_TOKEN")
+	if token == "" {
+		log.Fatal("Umgebungsvariable DISCORD_TOKEN ist nicht gesetzt")
+	}
+
+	dg, err := discordgo.New("Bot " + token)
+	if err != nil {
+		log.Fatal("Fehler beim Erstellen der Discord-Session:", err)
+	}
+
+	targetChannelName := os.Getenv("TARGET_CHANNEL_NAME")
+	if targetChannelName == "" {
+		targetChannelName = "threads-und-diskussionen"
+	}
+
+	dg.AddHandler(func(s *discordgo.Session, t *discordgo.ThreadCreate) {
+		onThreadCreate(s, t, targetChannelName)
+	})
+
+	// GUILDS-Intent enthält THREAD_CREATE-Events
+	dg.Identify.Intents = discordgo.IntentsGuilds
+
+	if err = dg.Open(); err != nil {
+		log.Fatal("Fehler beim Öffnen der Verbindung:", err)
+	}
+	defer dg.Close()
+
+	fmt.Println("Bot läuft. CTRL+C zum Beenden.")
+
+	sc := make(chan os.Signal, 1)
+	signal.Notify(sc, syscall.SIGINT, syscall.SIGTERM, os.Interrupt)
+	<-sc
+}
+
+func onThreadCreate(s *discordgo.Session, t *discordgo.ThreadCreate, targetChannelName string) {
+	// Neu erstellte Threads haben NewlyCreated == true.
+	// Ohne diese Prüfung feuert das Event auch beim Bot-Start für bestehende Threads.
+	if !t.NewlyCreated {
+		return
+	}
+
+	channels, err := s.GuildChannels(t.GuildID)
+	if err != nil {
+		log.Println("Fehler beim Abrufen der Channels:", err)
+		return
+	}
+
+	var targetChannelID string
+	for _, ch := range channels {
+		if ch.Name == targetChannelName {
+			targetChannelID = ch.ID
+			break
+		}
+	}
+
+	if targetChannelID == "" {
+		log.Printf("Channel #%s nicht gefunden\n", targetChannelName)
+		return
+	}
+
+	threadLink := fmt.Sprintf("https://discord.com/channels/%s/%s", t.GuildID, t.ID)
+	message := fmt.Sprintf("Neuer Thread: **%s**\n%s", t.Name, threadLink)
+
+	if _, err = s.ChannelMessageSend(targetChannelID, message); err != nil {
+		log.Println("Fehler beim Senden der Nachricht:", err)
+	}
+}