fixed dockerfile issue

Dockerfile

@@ -1,20 +1,28 @@
+# Start from the latest golang base image
 FROM golang:alpine
 
+# Add Maintainer Info
 LABEL org.opencontainers.image.source=https://github.com/chefgs/linktoqr
 LABEL description="This container image can be used to generate QR from the given URL or Text."
 LABEL org.opencontainers.image.licenses=MIT
 
-# Set necessary environmet variables needed for our image
+# Set necessary environment variables needed for our image
 ENV CGO_ENABLED=0 \
-    GOOS=linux
+    GOOS=linux \
+    GO111MODULE=on
 
-WORKDIR $GOPATH/src/linktoqr
+# Move to working directory /linktoqr
+WORKDIR /linktoqr
 
-COPY ./*go* .
+# Copy and download dependency using go mod
+COPY go.mod .
+RUN go mod tidy
 
-RUN go build -o /linktoqr 
+# Copy the code into the container
+COPY . .
 
 # Export necessary port
 EXPOSE 1718
 
-CMD ["/linktoqr"]
+# Command to run the executable
+CMD ["go", "run", "./..."]