Go

Go projects fall back to Nixpacks, which detects go.mod, uses the Go version from it, builds the module and runs the resulting binary.

Listen on $PORT

package main

import (
	"log"
	"net/http"
	"os"
)

func main() {
	port := os.Getenv("PORT")
	if port == "" {
		port = "8080"
	}
	http.HandleFunc("/health", func(w http.ResponseWriter, r *http.Request) { w.Write([]byte("ok")) })
	log.Fatal(http.ListenAndServe(":"+port, nil))
}

":"+port listens on all interfaces, which is what you want in a container.

Several binaries

If main packages live under cmd/, set a custom build command and start command, for example go build -o app ./cmd/server and ./app.

Using a Dockerfile

A multi-stage Dockerfile gives the smallest image:

FROM golang:1.25 AS build
WORKDIR /src
COPY go.mod go.sum ./
RUN go mod download
COPY . .
RUN CGO_ENABLED=0 go build -trimpath -ldflags="-s -w" -o /app ./cmd/server

FROM gcr.io/distroless/static-debian12:nonroot
COPY --from=build /app /app
ENV PORT=8080
EXPOSE 8080
ENTRYPOINT ["/app"]