.gitpod.Dockerfile: Auto-fetch Go and goyacc vers

In this commit we auto-fetch Go version from go.mod
and goyacc version from Makefile in the Prometheus repo.

Signed-off-by: Mohamed Awnallah <mohamedmohey2352@gmail.com>

.gitpod.Dockerfile

@@ -1,15 +1,33 @@
 FROM gitpod/workspace-full
 
+# Set Node.js version as an environment variable.
 ENV CUSTOM_NODE_VERSION=16
-ENV CUSTOM_GO_VERSION=1.19
-ENV GOPATH=$HOME/go-packages
-ENV GOROOT=$HOME/go
-ENV PATH=$GOROOT/bin:$GOPATH/bin:$PATH
 
+# Install and use the specified Node.js version via nvm.
 RUN bash -c ". .nvm/nvm.sh && nvm install ${CUSTOM_NODE_VERSION} && nvm use ${CUSTOM_NODE_VERSION} && nvm alias default ${CUSTOM_NODE_VERSION}"
 
+# Ensure nvm uses the default Node.js version in all new shells.
 RUN echo "nvm use default &>/dev/null" >> ~/.bashrc.d/51-nvm-fix
-RUN curl -fsSL https://dl.google.com/go/go${GO_VERSION}.linux-amd64.tar.gz | tar xzs \
-    && printf '%s\n' 'export GOPATH=/workspace/go' \
-                      'export PATH=$GOPATH/bin:$PATH' > $HOME/.bashrc.d/300-go
 
+# Remove any existing Go installation in $HOME path.
+RUN rm -rf $HOME/go $HOME/go-packages
+
+# Export go environment variables.
+RUN echo "export GOPATH=/workspace/go" >> ~/.bashrc.d/300-go && \
+    echo "export GOBIN=\$GOPATH/bin" >> ~/.bashrc.d/300-go && \
+    echo "export GOROOT=${HOME}/go" >> ~/.bashrc.d/300-go && \
+    echo "export PATH=\$GOROOT/bin:\$GOBIN:\$PATH" >> ~/.bashrc
+
+# Reload the environment variables to ensure go environment variables are
+# available in subsequent commands.
+RUN bash -c "source ~/.bashrc && source ~/.bashrc.d/300-go"
+
+# Fetch the Go version dynamically from the Prometheus go.mod file and Install Go in $HOME path.
+RUN export CUSTOM_GO_VERSION=$(curl -sSL "https://raw.githubusercontent.com/prometheus/prometheus/main/go.mod" | awk '/^go/{print $2".0"}') && \
+    curl -fsSL "https://dl.google.com/go/go${CUSTOM_GO_VERSION}.linux-amd64.tar.gz" | \
+    tar -xz -C $HOME
+
+# Fetch the goyacc parser version dynamically from the Prometheus Makefile
+# and install it globally in $GOBIN path.
+RUN GOYACC_VERSION=$(curl -fsSL "https://raw.githubusercontent.com/prometheus/prometheus/main/Makefile" | awk -F'=' '/GOYACC_VERSION \?=/{gsub(/ /, "", $2); print $2}') && \
+    go install "golang.org/x/tools/cmd/goyacc@${GOYACC_VERSION}"