build: modernize Go usage

This commit modernizes Go usage. This was done with:

go run golang.org/x/tools/gopls/internal/analysis/modernize/cmd/modernize@latest -fix -test ./...

Then files needed to be `go fmt`ed and a few comments needed to be
restored.

The modernizations include replacing

- if/else conditional assignment by a call to the built-in min or max functions added in go1.21
- sort.Slice(x, func(i, j int) bool) { return s[i] < s[j] } by a call to slices.Sort(s), added in go1.21
- interface{} by the 'any' type added in go1.18
- append([]T(nil), s...) by slices.Clone(s) or slices.Concat(s), added in go1.21
- loop around an m[k]=v map update by a call to one of the Collect, Copy, Clone, or Insert functions from the maps package, added in go1.21
- []byte(fmt.Sprintf...) by fmt.Appendf(nil, ...), added in go1.19
- append(s[:i], s[i+1]...) by slices.Delete(s, i, i+1), added in go1.21
- a 3-clause for i := 0; i < n; i++ {} loop by for i := range n {}, added in go1.22

fs/rc/jobs/job.go

@@ -6,6 +6,7 @@ import (
 	"errors"
 	"fmt"
 	"runtime/debug"
+	"slices"
 	"sync"
 	"sync/atomic"
 	"time"
@@ -79,7 +80,7 @@ func (job *Job) removeListener(fn *func()) {
 	defer job.mu.Unlock()
 	for i, ln := range job.listeners {
 		if ln == fn {
-			job.listeners = append(job.listeners[:i], job.listeners[i+1:]...)
+			job.listeners = slices.Delete(job.listeners, i, i+1)
 			return
 		}
 	}

fs/rc/params.go

@@ -6,6 +6,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"maps"
 	"math"
 	"net/http"
 	"strconv"
@@ -15,7 +16,7 @@ import (
 )
 
 // Params is the input and output type for the Func
-type Params map[string]interface{}
+type Params map[string]any
 
 // ErrParamNotFound - this is returned from the Get* functions if the
 // parameter isn't found along with a zero value of the requested
@@ -70,7 +71,7 @@ func IsErrParamInvalid(err error) bool {
 // out should be a pointer type
 //
 // This isn't a very efficient way of dealing with this!
-func Reshape(out interface{}, in interface{}) error {
+func Reshape(out any, in any) error {
 	b, err := json.Marshal(in)
 	if err != nil {
 		return fmt.Errorf("Reshape failed to Marshal: %w", err)
@@ -85,9 +86,7 @@ func Reshape(out interface{}, in interface{}) error {
 // Copy shallow copies the Params
 func (p Params) Copy() (out Params) {
 	out = make(Params, len(p))
-	for k, v := range p {
-		out[k] = v
-	}
+	maps.Copy(out, p)
 	return out
 }
 
@@ -95,7 +94,7 @@ func (p Params) Copy() (out Params) {
 //
 // If the parameter isn't found then error will be of type
 // ErrParamNotFound and the returned value will be nil.
-func (p Params) Get(key string) (interface{}, error) {
+func (p Params) Get(key string) (any, error) {
 	value, ok := p[key]
 	if !ok {
 		return nil, ErrParamNotFound(key)
@@ -241,7 +240,7 @@ func (p Params) GetBool(key string) (bool, error) {
 //
 // If the parameter isn't found then error will be of type
 // ErrParamNotFound and out will be unchanged.
-func (p Params) GetStruct(key string, out interface{}) error {
+func (p Params) GetStruct(key string, out any) error {
 	value, err := p.Get(key)
 	if err != nil {
 		return err
@@ -262,7 +261,7 @@ func (p Params) GetStruct(key string, out interface{}) error {
 
 // GetStructMissingOK works like GetStruct but doesn't return an error
 // if the key is missing
-func (p Params) GetStructMissingOK(key string, out interface{}) error {
+func (p Params) GetStructMissingOK(key string, out any) error {
 	_, ok := p[key]
 	if !ok {
 		return nil

fs/rc/params_test.go

@@ -109,7 +109,7 @@ func TestParamsGetString(t *testing.T) {
 
 func TestParamsGetInt64(t *testing.T) {
 	for _, test := range []struct {
-		value     interface{}
+		value     any
 		result    int64
 		errString string
 	}{
@@ -152,7 +152,7 @@ func TestParamsGetInt64(t *testing.T) {
 
 func TestParamsGetFloat64(t *testing.T) {
 	for _, test := range []struct {
-		value     interface{}
+		value     any
 		result    float64
 		errString string
 	}{
@@ -193,7 +193,7 @@ func TestParamsGetFloat64(t *testing.T) {
 
 func TestParamsGetDuration(t *testing.T) {
 	for _, test := range []struct {
-		value     interface{}
+		value     any
 		result    time.Duration
 		errString string
 	}{
@@ -244,7 +244,7 @@ func TestParamsGetDuration(t *testing.T) {
 
 func TestParamsGetBool(t *testing.T) {
 	for _, test := range []struct {
-		value     interface{}
+		value     any
 		result    bool
 		errString string
 	}{

fs/rc/rcserver/metrics_test.go

@@ -41,7 +41,7 @@ func TestMetrics(t *testing.T) {
 
 	// Test changing a couple options
 	stats.Bytes(500)
-	for i := 0; i < 30; i++ {
+	for range 30 {
 		require.NoError(t, stats.DeleteFile(context.Background(), 0))
 	}
 	stats.Errors(2)

fs/rc/rcserver/rcserver_test.go

@@ -69,7 +69,7 @@ func TestRcServer(t *testing.T) {
 	// Do the simplest possible test to check the server is alive
 	// Do it a few times to wait for the server to start
 	var resp *http.Response
-	for i := 0; i < 10; i++ {
+	for range 10 {
 		resp, err = http.Get(testURL + "file.txt")
 		if err == nil {
 			break
@@ -843,7 +843,7 @@ func TestContentTypeJSON(t *testing.T) {
 }
 
 func normalizeJSON(t *testing.T, jsonStr string) string {
-	var jsonObj map[string]interface{}
+	var jsonObj map[string]any
 	err := json.Unmarshal([]byte(jsonStr), &jsonObj)
 	require.NoError(t, err, "JSON unmarshalling failed")
 	normalizedJSON, err := json.Marshal(jsonObj)