Go - migetpacks

Detection

migetpacks detects Go when any of these files are present in your project root:

go.mod
Godeps/Godeps.json
glide.yaml

Version Detection

Go version is resolved in this order:

Priority	Source	Example
1	`GO_VERSION` env var	`GO_VERSION=1.23`
2	`.go-version` file	`1.25.0`
3	`go` directive in `go.mod`	`go 1.23`
4	Default	`1.25.0`

Build Process

migetpacks generates a multi-stage Dockerfile that produces a static binary:

# Builder stage
FROM golang:1.25 AS builder
WORKDIR /build

# Go build environment (static linking)
ENV CGO_ENABLED=0
ENV GOOS=linux

# Layer 1: Copy go.mod/go.sum for layer caching
COPY go.mod go.sum* ./

# Layer 2: Download dependencies (CACHED when go.mod unchanged)
RUN go mod download

# Layer 3: Copy source code
COPY . .

# Layer 4: Build static binary and cleanup
RUN go build -ldflags="-s -w" -o /build/myapp . \
    && rm -rf .git *.go go.mod go.sum vendor/

# Runtime stage
FROM debian:bookworm-slim
RUN apt-get update && apt-get install -y ca-certificates
WORKDIR /app
COPY --from=builder /build /app

Static Linking

Go builds use CGO_ENABLED=0 by default, producing fully static binaries that run on minimal base images. The linker flags -s -w strip debug information for smaller binaries.

Module Name and Binary Detection

The binary name is automatically derived from the module name in go.mod:

module github.com/user/myapp produces binary myapp
Falls back to app if detection fails

Package Spec

You can specify which packages to build using the //+heroku install comment in go.mod:

module github.com/user/myapp

// +heroku install ./cmd/api ./cmd/worker

go 1.23

Without this directive, go build . is used (builds the package in the current directory). For multiple packages, binaries are placed in /build/bin/:

RUN go build -ldflags="-s -w" -o /build/bin/ ./cmd/...

Build Hooks

migetpacks supports pre- and post-compile hooks:

bin/go-pre-compile - Runs before go build
bin/go-post-compile - Runs after go build

golang-migrate

If github.com/golang-migrate/migrate is detected in go.mod, the migrate CLI tool is automatically installed in the builder stage.

Linker Symbols

Set custom linker symbols using environment variables:

-e GO_LINKER_SYMBOL=main.version -e GO_LINKER_VALUE=1.0.0

This adds -X main.version=1.0.0 to the linker flags.

Run Command

The default run command is determined in this order:

Priority	Source	Command
1	`RUN_COMMAND` env var	User-specified
2	`web:` in Procfile	From Procfile
3	Default	`./app` (or `./myapp` based on module name)

Binary names in Procfiles are automatically prefixed with ./ if they don’t already have a path prefix.

Caching

Docker Layer Caching

Dependencies are downloaded in a separate layer. go mod download is only re-run when go.mod or go.sum changes.

BuildKit Cache Mounts

When BUILD_CACHE_DIR is configured, BuildKit cache mounts are used:

Cache Path	Contents
`/cache/go`	Go module cache (`/go/pkg/mod`) and build cache (`~/.cache/go-build`)

Registry Cache

Use CACHE_IMAGE to push/pull BuildKit inline cache layers to a registry for cross-build caching.

DHI Support

Go is supported with Docker Hardened Images (requires version 1.22 or later).

Stage	Image
Build	`dhi.io/golang:{version}-dev`
Runtime	`dhi.io/golang:{version}`

DHI images for Go require minimum patch versions: 1.22.12, 1.23.7, or 1.24.1+. Older patch versions within these minor releases are not available.

The DHI runtime image is distroless with no shell. Since Go produces static binaries, this works without any special handling.

Go Toolchain in Runtime

If you need the Go toolchain available at runtime (for plugins, go run, etc.):

-e GO_INSTALL_TOOLS_IN_IMAGE=true

This copies /usr/local/go from the builder to the runtime image.

Example

docker run --rm \
  -v /path/to/app:/workspace/source \
  -v /var/run/docker.sock:/var/run/docker.sock \
  -e OUTPUT_IMAGE=my-go-app:latest \
  miget/migetpacks:latest

With Custom Options

docker run --rm \
  -v /path/to/app:/workspace/source \
  -v /var/run/docker.sock:/var/run/docker.sock \
  -e OUTPUT_IMAGE=registry.io/app:v1 \
  -e GO_VERSION=1.23 \
  -e GO_LINKER_SYMBOL=main.version \
  -e GO_LINKER_VALUE=1.2.3 \
  -e USE_DHI=true \
  miget/migetpacks:latest

Multi-Binary Project

docker run --rm \
  -v /path/to/app:/workspace/source \
  -v /var/run/docker.sock:/var/run/docker.sock \
  -e OUTPUT_IMAGE=registry.io/app:v1 \
  -e RUN_COMMAND="./bin/api" \
  miget/migetpacks:latest

With // +heroku install ./cmd/api ./cmd/worker in go.mod, both binaries are available at /app/bin/api and /app/bin/worker.

Getting Started

Guides

Configuration

Languages

Deploying

Reference

Go

Detection

Version Detection

Build Process

Static Linking

Module Name and Binary Detection

Package Spec

Build Hooks

golang-migrate

Linker Symbols

Run Command

Caching

Docker Layer Caching

BuildKit Cache Mounts

Registry Cache

DHI Support

Go Toolchain in Runtime

Example

With Custom Options

Multi-Binary Project

​Detection

​Version Detection

​Build Process

​Static Linking

​Module Name and Binary Detection

​Package Spec

​Build Hooks

​golang-migrate

​Linker Symbols

​Run Command

​Caching

​Docker Layer Caching

​BuildKit Cache Mounts

​Registry Cache

​DHI Support

​Go Toolchain in Runtime

​Example

​With Custom Options

​Multi-Binary Project

Detection

Version Detection

Build Process

Static Linking

Module Name and Binary Detection

Package Spec

Build Hooks

golang-migrate

Linker Symbols

Run Command

Caching

Docker Layer Caching

BuildKit Cache Mounts

Registry Cache

DHI Support

Go Toolchain in Runtime

Example

With Custom Options

Multi-Binary Project