MacOS环境下构建Golang Docker镜像时如何解决/bin/sh: 1: source: not found错误？

Hey there! Let's break down what's going wrong here and fix it step by step.

First, let's diagnose the two main issues #

1. Why the source/. command fails (or says "file not found")
   Docker uses /bin/sh as the default shell for RUN commands, and while . is the POSIX-compatible alternative to Bash's source, your bigger problem is timing: you're trying to load the .env file before you've copied it into the container! Look at your Dockerfile order: RUN . .env comes way before COPY . ./, so the file doesn't exist in the container at that point.

2. Environment variables don't persist across RUN layers
   Each RUN command runs in a separate shell session. Even if you loaded .env correctly in one RUN, those variables won't be available in subsequent RUN commands unless you chain everything in a single shell session.

Solution 1: Load .env during build (if you need variables for build steps) #

If you need the environment variables to run commands like go build or go mod download, adjust your Dockerfile to copy the .env first, then chain all dependent commands in one Bash session:

FROM golang:latest
WORKDIR /go/src/todo_list

# First, copy your .env file into the container (critical!)
COPY .env ./

# Run all commands that need the env vars in a single Bash session
RUN /bin/bash -c "source .env && go mod download && go mod verify"

# Copy the rest of your code
COPY go.mod ./
COPY go.sum ./
COPY . ./

WORKDIR /go/src/todo_list/cmd/main
EXPOSE 9010
RUN go build main.go

CMD ["./main", "-migrate"]

Solution 2: Load .env at runtime (recommended for most cases) #

If your environment variables are only needed when the Go app runs (not during build), you don't need to touch .env in the Dockerfile at all. Instead, pass the variables when starting the container:

First, clean up your Dockerfile:

FROM golang:latest
WORKDIR /go/src/todo_list

COPY go.mod ./
COPY go.sum ./
RUN go mod download

COPY . ./
WORKDIR /go/src/todo_list/cmd/main
EXPOSE 9010
RUN go mod verify
RUN go build main.go

CMD ["./main", "-migrate"]

Then run your container with the --env-file flag to load your local .env:

docker run --env-file .env -p 9010:9010 your-image-name

This is better because:

• Sensitive env vars aren't baked into your image
• You can use different .env files for development/production without rebuilding the image
• Add .env to your .dockerignore to avoid accidentally copying it into the image

Bonus: If your Go app reads .env directly #

If you're using a library like github.com/joho/godotenv to load .env in your code, just make sure to copy the file into the container and point your app to it:

# Add this line after COPY . ./
COPY .env ./cmd/main/

Then your app can load it normally at runtime.

内容的提问来源于stack exchange，提问作者JiwanJeon94