Docker : failed to compute cache key

I am trying to build a docker image for my sample-go app.
I am running it from the sample-app folder itself and using the goland editor's terminal. But the build is failing and giving me certain errors.

My docker file looks like this:

FROM alpine:latest

RUN mkdir -p /src/build
WORKDIR /src/build

RUN apk add --no-cache tzdata ca-certificates

COPY ./configs /configs
COPY main /main

EXPOSE 8000

CMD ["/main"]

command for building:

docker build --no-cache --progress=plain  - < Dockerfile

Error And Logs:

#1 [internal] load build definition from Dockerfile
#1 sha256:8bb9ee83603259cf748d90ce42602f12527fa720d7417da22799b2ad4e503497
#1 transferring dockerfile: 222B done
#1 DONE 0.0s

#2 [internal] load .dockerignore
#2 sha256:f93d938488588cd0e0a94d9d343fe69dcfd28d0cb1da95ad7aab00aac50235c3
#2 transferring context: 2B done
#2 DONE 0.0s

#3 [internal] load metadata for docker.io/library/alpine:latest
#3 sha256:13549c58a76bcb5dac9d52bc368a8fb6b5cf7659f94e3fa6294917b85546978d
#3 DONE 0.0s

#10 [1/6] FROM docker.io/library/alpine:latest
#10 sha256:d20daa00e252bfb345a1b4f53b6bb332aafe702d8de5e583a76fcd09ba7ea1c1
#10 CACHED

#7 [internal] load build context
#7 sha256:0f7a8a6082a837c139acc2855e1b745bba9f28cc96709d45cd0b7be42442c0e8
#7 transferring context: 2B done
#7 DONE 0.0s

#4 [2/6] RUN mkdir -p /src/build
#4 sha256:b9fa3007a44471d47414dd29b3ff07ead6af28ede820a2b4bae0ce84cf2c5a83
#4 CACHED

#5 [3/6] WORKDIR /src/build
#5 sha256:b2ec58a365fdd74c4f9030b0caff2e2225eea33617da306678ad037fce675388
#5 CACHED

#6 [4/6] RUN apk add --no-cache tzdata ca-certificates
#6 sha256:0966097abf956d5781bc2330d49cf715cd52c3807e8fedfff07dec50907ff03b
#6 CACHED

#9 [6/6] COPY main /main
#9 sha256:f4b81960427c014a020361bea0903728f289e1d796892fe0adc6409434f3ca76
#9 ERROR: "/main" not found: not found

#8 [5/6] COPY ./configs /configs
#8 sha256:630f272dd60dd307f40dbbdaef277ee0dfc24b71fa11e10a3b8efd64d3c05086
#8 ERROR: "/configs" not found: not found

#4 [2/6] RUN mkdir -p /src/build
#4 sha256:b9fa3007a44471d47414dd29b3ff07ead6af28ede820a2b4bae0ce84cf2c5a83
#4 DONE 0.2s
------
 > [5/6] COPY ./configs /configs:
------
------
 > [6/6] COPY main /main:
------
failed to compute cache key: "/main" not found: not found

PS: I am not able to find where is the problem? Help Please

This is a basic mistake.

• COPY ./configs /configs: copy the folder configs from the host to the Docker image.
• COPY main /main: copy the executable file main from the host to the Docker image.

The problems are:

• The base Docker images do not have these folders /configs, /main. You must create them manually (Docker understood your command this way).
• But I have some advice:
  • Create 2 Docker images for 2 purposes: build, production.
  • Copy the source code into Docker builder image which is use for building your app.
  • Copy necessary output files from the Docker builder image into the Docker production image.

In my case I missed the folder entry in .dockerignore file. Do something like that.

**/*
!docker-images
!configs
!main

The two folders /main and /configs does not exist.

The COPY command can't copy into this folders.

1. Solution

Create the folders on build

RUN mkdir -p /main

RUN mkdir -p /configs

And than use COPY

2. Solution

1. Try to build without COPY and CMD

2. Than run the the new image

3. exec into running container with bash or sh

4. Create the folders

5. Exit exec container

6. Create a new image of the running container with docker run commit

7. Stop the container and delete it

8. Build again with your new image and include COPY and CMD

In my case, the issue was the connected vpn/proxy network from my machine.
It worked after I disconnecting the vpn/proxy network.