Using upstream caddy instead of compiling from source

Signed-off-by: Ondrej Kubik <ondrej.kubik@canonical.com>

snapcraft.yaml

@@ -130,27 +130,15 @@ parts:
         source: snap-src
         plugin: dump
 
-    go:
-        plugin: nil
-        prepare: |
-          gov=$(echo "$(go version | awk '{ print $3}' | sed 's/^..//') 1.7" | awk '{if ($1 < $2) print "old";}')
-          echo "$(go version)"
-          if [ "${gov}" = "old" ]; then \
-              echo "updating to new go"; \
-              curl https://storage.googleapis.com/golang/go1.9.2.linux-amd64.tar.gz -o go1.9.2.linux-amd64.tar.gz; \
-              tar -xvf go1.9.2.linux-amd64.tar.gz; \
-              rm -rf /usr/lib/go; \
-              mv go /usr/lib/; \
-              ln -sf ../lib/go/bin/go /usr/bin/go; \
-          fi
-
     caddy:
-        plugin: go
-        go-importpath: github.com/mholt/caddy
-        source: https://github.com/mholt/caddy.git
-        source-type: git
-        source-commit: 53e117802fedd5915eeb32907873d8786a4b2936
-        after:
-            - go
-        prime:
-            - bin/caddy
+        plugin: dump
+        source: https://caddyserver.com/download/linux/amd64?plugins=
+        source-type: tar
+        organize:
+          caddy: bin/caddy
+          CHANGES.txt: CADDY_CHANGES.txt
+          EULA.txt: CADDY_EULA.txt
+          LICENSES.txt: CADDY_LICENSES.txt
+          README.txt: CADDY_README.txt
+        stage:
+          - -init