Add option to use Docker container to run Asynqmon

Makefile

@@ -1,11 +1,24 @@
+.PHONY: assets go_binary build docker
+
+NODE_MODULES_PATH = $(PWD)/ui/node_modules
+
+# Checking for a node_modules folder before building.
 assets:
+	@if [ -d "$(NODE_MODULES_PATH)" ]; then cd ./ui && yarn install; fi
 	cd ./ui && yarn build
 
-# TODO: Update this once go1.16 is released.
-go_binary:
-	go1.16rc1 build -o asynqmon .
+# Build go binary.
+go_binary: assets
+	go build -o asynqmon .
 
 # Target to build a release binary.
-build: assets go_binary
+build: go_binary
 
+# Build image and run Asynqmon server (with default settings).
+docker:
+	docker build -t asynqmon .
+	docker run --rm \
+		--name asynqmon \
+		-p 8080:8080 \
+		asynqmon