Improved CI pipeline and added version information

.gitlab-ci-docs.yml

+# This is the CI file for GitLab Pages
+
 pages:
   stage: deploy
   image: python:3.7-alpine
+
   before_script:
     # TODO: we should consider also version locking these packages:
     #  + everything will work in the future
     #  - we wont see any future improvements by mkdocs or mkdocs-material
     - pip install mkdocs
     - pip install mkdocs-material
+
   script:
   - mkdocs build
-  - mv site public
-  - mv binaries public/
+  - mv site public # move mkdocs output to public
+  - mv binaries public/ # move binaries from the build stage to public
+  
   artifacts:
     paths:
     - public

.gitlab-ci-server.yml

+# This is the CI file for the stream-tv-server
+
 server:
   stage: build
   image: golang:1.12
-  variables:
-    LDFLAGS: -s -X code.fbi.h-da.de/simons-nzse-2/stream-tv/pkg/twitch.ClientID=${TWITCH_CLIENT_ID}
+
+  # TWITCH_CLIENT_ID is supplied via the GitLab CI/CD environment variables. This way only project owners can see the private key.
+  
+  before_script:
+    - VERSION=$(git describe --always --long --dirty)
+    - export LDFLAGS="-s -X stream-tv/pkg/twitch.ClientID=$TWITCH_CLIENT_ID -X stream-tv/cmd/stream-tv-server/main.version=$VERSION"
+    - go mod download
+    - echo "building $VERSION"
+
   script:
-    - env GOOS=darwin   GOARCH=386    go build -ldflags "${LDFLAGS}" -o binaries/darwin-x86/stream-tv-server          ./cmd/stream-tv-server
-    - env GOOS=darwin   GOARCH=amd64  go build -ldflags "${LDFLAGS}" -o binaries/darwin-x86_64/stream-tv-server       ./cmd/stream-tv-server
+    - env GOOS=darwin   GOARCH=386    go build -ldflags "$LDFLAGS" -o binaries/darwin-x86/stream-tv-server          ./cmd/stream-tv-server
+    - env GOOS=darwin   GOARCH=amd64  go build -ldflags "$LDFLAGS" -o binaries/darwin-x86_64/stream-tv-server       ./cmd/stream-tv-server
 
-    - env GOOS=linux    GOARCH=386    go build -ldflags "${LDFLAGS}" -o binaries/linux-x86/stream-tv-server           ./cmd/stream-tv-server
-    - env GOOS=linux    GOARCH=amd64  go build -ldflags "${LDFLAGS}" -o binaries/linux-x86_64/stream-tv-server        ./cmd/stream-tv-server
-    - env GOOS=linux    GOARCH=arm    go build -ldflags "${LDFLAGS}" -o binaries/linux-arm/stream-tv-server           ./cmd/stream-tv-server
-    - env GOOS=linux    GOARCH=arm64  go build -ldflags "${LDFLAGS}" -o binaries/linux-arm64/stream-tv-server         ./cmd/stream-tv-server
+    - env GOOS=linux    GOARCH=386    go build -ldflags "$LDFLAGS" -o binaries/linux-x86/stream-tv-server           ./cmd/stream-tv-server
+    - env GOOS=linux    GOARCH=amd64  go build -ldflags "$LDFLAGS" -o binaries/linux-x86_64/stream-tv-server        ./cmd/stream-tv-server
+    - env GOOS=linux    GOARCH=arm    go build -ldflags "$LDFLAGS" -o binaries/linux-arm/stream-tv-server           ./cmd/stream-tv-server
+    - env GOOS=linux    GOARCH=arm64  go build -ldflags "$LDFLAGS" -o binaries/linux-arm64/stream-tv-server         ./cmd/stream-tv-server
 
-    - env GOOS=windows  GOARCH=386    go build -ldflags "${LDFLAGS}" -o binaries/windows-x86/stream-tv-server.exe     ./cmd/stream-tv-server
-    - env GOOS=windows  GOARCH=amd64  go build -ldflags "${LDFLAGS}" -o binaries/windows-x86_64/stream-tv-server.exe  ./cmd/stream-tv-server
+    - env GOOS=windows  GOARCH=386    go build -ldflags "$LDFLAGS" -o binaries/windows-x86/stream-tv-server.exe     ./cmd/stream-tv-server
+    - env GOOS=windows  GOARCH=amd64  go build -ldflags "$LDFLAGS" -o binaries/windows-x86_64/stream-tv-server.exe  ./cmd/stream-tv-server
 
   artifacts:
     paths: