docker build failure for examples/out_multiinstance/Dockerfile

Follow https://github.com/fluent/fluent-bit-go/tree/master/examples/out_multiinstance and hit No rule to make target 'all'.

~/fluent-bit-go$ sudo docker build . -t fluent-bit-multiinstance -f examples/out_multiinstance/Dockerfile
Sending build context to Docker daemon 164.9kB
Step 1/12 : FROM golang:1.14 as gobuilder
---> 21a5635903d6
Step 2/12 : WORKDIR /root
---> Using cache
---> cac906ec79de
Step 3/12 : ENV GOOS=linux GOARCH=amd64
---> Using cache
---> bf8c66726cbd
Step 4/12 : COPY / /root/
---> Using cache
---> 307205a0b494
Step 5/12 : RUN go mod edit -replace github.com/fluent/fluent-bit-go=github.com/fluent/fluent-bit-go@master
---> Using cache
---> a8571dbaaa4c
Step 6/12 : RUN go mod download & make all
---> Running in 1ba930ea937b
make: *** No rule to make target 'all'. Stop.
The command '/bin/sh -c go mod download & make all' returned a non-zero code: 2