feat(gotester): added gotester for go build speedups

README.md

@@ -3,3 +3,6 @@ In various places across the ILF ecosystem we need custom built images. Quite of
 Image: Chart Validator
 Description: Kustomize, Helm, GCloud SDK and Kubeconform. For easy chart validation.
 
+Image: Go Tester
+Description: Go 1.25, golangci-lint, Atlas CLI, and PostgreSQL client. Pre-built image for running Go unit tests, mock-service tests, and linting in CI.
+

gotester/Dockerfile

@@ -0,0 +1,36 @@
+FROM golang:1.25-alpine
+
+# System dependencies needed by both go-test and mock-tester CI workflows:
+#   bash     - shell scripts in CI steps
+#   bc       - floating-point coverage threshold comparison
+#   curl     - downloading tools (Atlas CLI)
+#   git      - Go modules, golangci-lint VCS checks
+#   grep     - GNU grep with -P (PCRE) for extracting coverage thresholds
+#   make     - mock service Makefiles
+#   postgresql17-client - pg_isready to wait for Postgres service containers
+RUN apk add --no-cache \
+    bash \
+    bc \
+    curl \
+    git \
+    grep \
+    make \
+    postgresql17-client
+
+# golangci-lint v2.5.0 — used by both mock-tester and linting workflows
+# Installed from versioned release artifact with checksum verification.
+ARG GOLANGCI_LINT_VERSION=2.5.0
+ARG GOLANGCI_LINT_SHA256=c77313a77e19b06123962c411d9943cc0d092bbec76b956104d18964e274902e
+RUN curl -sSfL "https://github.com/golangci/golangci-lint/releases/download/v${GOLANGCI_LINT_VERSION}/golangci-lint-${GOLANGCI_LINT_VERSION}-linux-amd64.tar.gz" \
+      -o /tmp/golangci-lint.tar.gz \
+    && echo "${GOLANGCI_LINT_SHA256}  /tmp/golangci-lint.tar.gz" | sha256sum -c - \
+    && tar -xzf /tmp/golangci-lint.tar.gz -C /tmp \
+    && mv /tmp/golangci-lint-${GOLANGCI_LINT_VERSION}-linux-amd64/golangci-lint /usr/local/bin/ \
+    && rm -rf /tmp/golangci-lint*
+
+# Atlas CLI — generates test migrations for backend/pacioli database schemas
+# Pinned to a specific version via ATLAS_VERSION; bump the ARG to upgrade.
+ARG ATLAS_VERSION=v1.2.0
+RUN ATLAS_VERSION=${ATLAS_VERSION} curl -sSf https://atlasgo.sh | sh
+
+WORKDIR /app

gotester/README.md

@@ -0,0 +1,47 @@
+# Go Tester
+
+Pre-built image for running Go unit tests, mock-service tests, and linting in the [interledger-app](https://github.com/interledger/interledger-app) CI pipeline.
+
+## What's inside
+
+| Tool | Version | Purpose |
+|------|---------|---------|
+| Go | 1.25 | Compile and test Go code |
+| golangci-lint | 2.5.0 | Lint all Go packages |
+| Atlas CLI | 1.2.0 | Generate database test migrations |
+| PostgreSQL 17 client | 17.x | `pg_isready` to wait for Postgres service containers |
+| GNU grep (PCRE) | — | Extract coverage thresholds with `-oP` |
+| bc | — | Floating-point coverage comparison |
+| make | — | Run mock-service Makefiles |
+| bash, git, curl | — | Standard CI utilities |
+
+## Replaces
+
+This single image replaces the tool-installation steps in two interledger-app workflow templates:
+
+- **`go-test-template.yml`** — `setup-go`, `Install Atlas CLI`, `pg_isready` wait loop
+- **`mock-tester.yml`** — `setup-go`, `golangci-lint-action`, Docker setup
+
+## Usage
+
+```yaml
+# GitHub Actions example
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    container:
+      image: ghcr.io/interledger/builders/gotester:latest
+    services:
+      postgres:
+        image: postgres:17
+    steps:
+      - uses: actions/checkout@v4
+      - run: go test -coverprofile=coverage.out ./go/backend/...
+```
+
+## Building locally
+
+```bash
+cd gotester
+docker build -t gotester .
+```