minimal example

12 files changed, 482 insertions, 0 deletions

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..ac21027
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,5 @@
+*~
+*.sw?
+/*.tar.gz
+/go-example
+/cover.html
diff --git a/.golangci.yml b/.golangci.yml
new file mode 100644
index 0000000..3fcf71e
--- /dev/null
+++ b/.golangci.yml
@@ -0,0 +1,56 @@
+---
+output:
+  sort-results: true
+
+run:
+  go: "1.23"
+
+linters-settings:
+  goimports:
+    local-prefixes: www.thenautilus.net/cgit
+
+  gci:
+    sections:
+      - standard
+      - default
+      - prefix(www.thenautilus.net/cgit)
+
+  misspell:
+    locale: "UK"
+
+  varnamelen:
+    ignore-names:
+      - ok
+      - w
+      - r
+
+  wsl:
+    # sometimes I really have to start a block with a comment!
+    allow-separated-leading-comment: true
+
+
+linters:
+  disable:
+    - ireturn # we should return concrete types, not interfaces, but I
+              # can't quite figure out how to do it...
+    - exhaustruct
+    - forbidigo
+    - depguard
+    - mnd
+    - nonamedreturns
+  presets:
+    - style
+    - bugs
+    - error
+    - format
+    - import
+    - module
+    - performance
+    - unused
+
+
+issues:
+  exclude:
+    - 'package should be `\w+_test`'
+    - 'package comment should not have leading space'
+    
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..1ee128f
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,34 @@
+TARGET = go-example
+RUN_MODE ?= development
+GO ?= go
+
+$(TARGET): */*.go go.sum
+	$(GO) build -o $@ ./cmd/main/
+
+.PHONY: test
+test:
+	$(GO) test -cover -coverprofile=coverage.out -v ./...
+	$(GO) tool cover -html=coverage.out -o cover.html
+	rm coverage.out
+
+.PHONY: lint
+lint: fmt
+	~/go/bin/golangci-lint run -v
+
+.PHONY: clean
+clean:
+	rm $(TARGET)
+
+.PHONY: fmt
+fmt:
+	~/go/bin/goimports -local www.thenautilus.net/cgit -w .
+	~/go/bin/gci write -s Standard -s Default -s 'Prefix(www.thenautilus.net/cgit)' .
+	~/go/bin/gofumpt -l -w .
+
+.PHONY: run
+run: $(TARGET)
+	./$(TARGET) --verbose --log-format=console $(ARGS)
+
+.PHONY: update
+update:
+	go get -u -t ./...
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..78052d6
--- /dev/null
+++ b/README.md
@@ -0,0 +1,27 @@
+# A Go example
+
+You'll need `go` 1.23 at least.
+
+There's a [`Makefile`](Makefile), so you can do:
+
+    $ make clean
+    $ make test
+    $ make
+    $ make run
+
+If you run:
+
+    go install golang.org/x/tools/cmd/goimports@latest
+    go install github.com/daixiang0/gci@latest
+    go install mvdan.cc/gofumpt@latest
+
+then you can do `make fmt` to format all the source files.
+
+If you `go install
+github.com/golangci/golangci-lint/cmd/golangci-lint@latest`, you can
+also do `make lint` to get a linting / critique of all the source
+files (`lint` runs `fmt` first, so you need to have installed the
+packages above as well).
+
+Note that the `Makefile` is *for development*, it's not used on
+production machines.
diff --git a/cmd/main/main.go b/cmd/main/main.go
new file mode 100644
index 0000000..ac7f788
--- /dev/null
+++ b/cmd/main/main.go
@@ -0,0 +1,33 @@
+package main
+
+import (
+	"fmt"
+	"os"
+
+	"www.thenautilus.net/cgit/go-example/config"
+	factorypkg "www.thenautilus.net/cgit/go-example/factory"
+	"www.thenautilus.net/cgit/go-example/logging"
+)
+
+func main() {
+	// this is the main binary, so the config file is in
+	// the same directory as the executable
+	config, err := config.GetMainConfig(".")
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "%s\n", err)
+		os.Exit(1)
+	}
+
+	log := logging.Logger(config.Logger)
+
+	log.Info().Object("config", &config).Msg("configuration")
+
+	factory := factorypkg.New(log, &config)
+
+	something := factory.Something()
+
+	err = something.DoSomething()
+	if err != nil {
+		log.Error().Err(err).Msg("Can't do the thing")
+	}
+}
diff --git a/config/config.go b/config/config.go
new file mode 100644
index 0000000..3c93d53
--- /dev/null
+++ b/config/config.go
@@ -0,0 +1,126 @@
+package config
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"path"
+	"strings"
+
+	"github.com/mitchellh/mapstructure"
+	"github.com/rs/zerolog"
+	"github.com/spf13/pflag"
+	"github.com/spf13/viper"
+)
+
+type LoggerConfig struct {
+	Verbose bool   `mapstructure:"verbose"`
+	Format  string `mapstructure:"format"`
+}
+
+func (c *LoggerConfig) MarshalZerologObject(e *zerolog.Event) {
+	e.
+		Bool("verbose", c.Verbose).
+		Str("format", c.Format)
+}
+
+type SomethingConfig struct {
+	Value int `mapstructure:"value"`
+}
+
+func (c *SomethingConfig) MarshalZerologObject(event *zerolog.Event) {
+	event.
+		Int("value", c.Value)
+}
+
+type MainConfig struct {
+	Something SomethingConfig `mapstructure:"something"`
+	Logger    LoggerConfig    `mapstructure:"logger"`
+
+	configFile string
+}
+
+func (c *MainConfig) MarshalZerologObject(event *zerolog.Event) {
+	event.
+		Str("config-file", c.configFile).
+		Object("logger", &c.Logger).
+		Object("something", &c.Something)
+}
+
+func addLoggerOptions() {
+	pflag.Bool("verbose", false, "log at debug level")
+	viper.BindPFlag("logger.verbose", pflag.Lookup("verbose")) //nolint:errcheck
+	pflag.String("log-format", "json", "logging format (json, console)")
+	viper.BindPFlag("logger.format", pflag.Lookup("log-format")) //nolint:errcheck
+}
+
+func addSomethingOptions() {
+	pflag.Int("something-value", 123, "value used to do something")
+	viper.BindPFlag("something.value", pflag.Lookup("something-value")) //nolint:errcheck
+	viper.BindEnv("something.value", "SOMETHING_VALUE")                 //nolint:errcheck
+}
+
+func addConfigFromFile(configRelPath string) error {
+	mode := os.Getenv("RUN_MODE")
+	if mode == "" {
+		mode = "development"
+	}
+
+	viper.SetConfigName("example." + mode)
+
+	myName, err := os.Executable()
+	if err == nil && !strings.HasPrefix(configRelPath, "/") {
+		myDir := path.Dir(myName)
+		viper.AddConfigPath(path.Join(myDir, configRelPath))
+	} else {
+		viper.AddConfigPath(configRelPath)
+	}
+
+	err = viper.ReadInConfig()
+	if err != nil {
+		var notFound viper.ConfigFileNotFoundError
+		if !errors.As(err, &notFound) {
+			return fmt.Errorf("failed to read config file at %s: %w", viper.ConfigFileUsed(), err)
+		}
+	}
+
+	return nil
+}
+
+func loadConfigFromFile(path string) (MainConfig, error) {
+	pathFromEnv := os.Getenv("EXAMPLE_CONFIG")
+	if pathFromEnv != "" {
+		path = pathFromEnv
+	}
+
+	err := addConfigFromFile(path)
+	if err != nil {
+		return MainConfig{}, err
+	}
+
+	var config MainConfig
+
+	err = viper.Unmarshal(&config, viper.DecodeHook(
+		mapstructure.ComposeDecodeHookFunc(
+			mapstructure.StringToTimeDurationHookFunc(),
+			mapstructure.StringToIPHookFunc(),
+		),
+	))
+	if err != nil {
+		return MainConfig{}, fmt.Errorf("failed to parse options: %w", err)
+	}
+
+	config.configFile = viper.ConfigFileUsed()
+
+	return config, nil
+}
+
+func GetMainConfig(path string) (MainConfig, error) {
+	addLoggerOptions()
+	addSomethingOptions()
+
+	pflag.Parse()
+	viper.BindPFlags(pflag.CommandLine) //nolint:errcheck
+
+	return loadConfigFromFile(path)
+}
diff --git a/example.development.json b/example.development.json
new file mode 100644
index 0000000..6c45101
--- /dev/null
+++ b/example.development.json
@@ -0,0 +1,5 @@
+{
+  "something": {
+    "value": 42
+  }
+}
diff --git a/factory/factory.go b/factory/factory.go
new file mode 100644
index 0000000..ae84911
--- /dev/null
+++ b/factory/factory.go
@@ -0,0 +1,33 @@
+package factory
+
+import (
+	"github.com/rs/zerolog"
+
+	"www.thenautilus.net/cgit/go-example/config"
+	"www.thenautilus.net/cgit/go-example/something"
+)
+
+type Factory struct {
+	something *something.Something
+
+	config *config.MainConfig
+	logger zerolog.Logger
+}
+
+func New(logger zerolog.Logger, config *config.MainConfig) Factory {
+	return Factory{
+		config: config,
+		logger: logger,
+	}
+}
+
+func (f *Factory) Something() *something.Something {
+	if f.something == nil {
+		something := something.New(
+			&f.config.Something,
+		)
+		f.something = &something
+	}
+
+	return f.something
+}
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..e4fcf67
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,29 @@
+module www.thenautilus.net/cgit/go-example
+
+go 1.23
+
+require (
+	github.com/fsnotify/fsnotify v1.7.0 // indirect
+	github.com/hashicorp/hcl v1.0.0 // indirect
+	github.com/magiconair/properties v1.8.7 // indirect
+	github.com/mattn/go-colorable v0.1.13 // indirect
+	github.com/mattn/go-isatty v0.0.19 // indirect
+	github.com/mitchellh/mapstructure v1.5.0 // indirect
+	github.com/pelletier/go-toml/v2 v2.2.2 // indirect
+	github.com/rs/zerolog v1.33.0 // indirect
+	github.com/sagikazarmark/locafero v0.4.0 // indirect
+	github.com/sagikazarmark/slog-shim v0.1.0 // indirect
+	github.com/sourcegraph/conc v0.3.0 // indirect
+	github.com/spf13/afero v1.11.0 // indirect
+	github.com/spf13/cast v1.6.0 // indirect
+	github.com/spf13/pflag v1.0.5 // indirect
+	github.com/spf13/viper v1.19.0 // indirect
+	github.com/subosito/gotenv v1.6.0 // indirect
+	go.uber.org/atomic v1.9.0 // indirect
+	go.uber.org/multierr v1.9.0 // indirect
+	golang.org/x/exp v0.0.0-20230905200255-921286631fa9 // indirect
+	golang.org/x/sys v0.18.0 // indirect
+	golang.org/x/text v0.14.0 // indirect
+	gopkg.in/ini.v1 v1.67.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000..02e8569
--- /dev/null
+++ b/go.sum
@@ -0,0 +1,68 @@
+github.com/coreos/go-systemd/v22 v22.5.0/go.mod h1:Y58oyj3AT4RCenI/lSvhwexgC+NSVTIJ3seZv2GcEnc=
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/fsnotify/fsnotify v1.7.0 h1:8JEhPFa5W2WU7YfeZzPNqzMP6Lwt7L2715Ggo0nosvA=
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+github.com/hashicorp/hcl v1.0.0/go.mod h1:E5yfLk+7swimpb2L/Alb/PJmXilQ/rhwaUYs4T20WEQ=
+github.com/magiconair/properties v1.8.7 h1:IeQXZAiQcpL9mgcAe1Nu6cX9LLw6ExEHKjN0VQdvPDY=
+github.com/magiconair/properties v1.8.7/go.mod h1:Dhd985XPs7jluiymwWYZ0G4Z61jb3vdS329zhj2hYo0=
+github.com/mattn/go-colorable v0.1.13 h1:fFA4WZxdEF4tXPZVKMLwD8oUnCTTo08duU7wxecdEvA=
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+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
diff --git a/logging/logging.go b/logging/logging.go
new file mode 100644
index 0000000..a24e13e
--- /dev/null
+++ b/logging/logging.go
@@ -0,0 +1,43 @@
+package logging
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"os"
+	"time"
+
+	"github.com/rs/zerolog"
+
+	"www.thenautilus.net/cgit/go-example/config"
+)
+
+// Logger returns a (optionally verbose) logger.
+func Logger(conf config.LoggerConfig) zerolog.Logger {
+	logLevel := zerolog.InfoLevel
+	if conf.Verbose {
+		logLevel = zerolog.DebugLevel
+	}
+
+	zerolog.TimestampFunc = func() time.Time {
+		return time.Now().UTC()
+	}
+
+	zerolog.InterfaceMarshalFunc = func(value interface{}) ([]byte, error) {
+		switch v := value.(type) {
+		case fmt.Stringer:
+			str := fmt.Sprintf("\"%s\"", v.String())
+
+			return []byte(str), nil
+		default:
+			return json.Marshal(value)
+		}
+	}
+
+	var w io.Writer = os.Stdout
+	if conf.Format == "console" {
+		w = zerolog.NewConsoleWriter()
+	}
+
+	return zerolog.New(w).Level(logLevel).With().Timestamp().Logger()
+}
diff --git a/something/something.go b/something/something.go
new file mode 100644
index 0000000..2516b2d
--- /dev/null
+++ b/something/something.go
@@ -0,0 +1,23 @@
+package something
+
+import (
+	"fmt"
+
+	"www.thenautilus.net/cgit/go-example/config"
+)
+
+type Something struct {
+	value int
+}
+
+func New(conf *config.SomethingConfig) Something {
+	return Something{
+		value: conf.Value,
+	}
+}
+
+func (s *Something) DoSomething() error {
+	fmt.Printf("the value is %d", s.value)
+
+	return nil
+}