all: apply suggestions from linter

List of changes,

* Remove unused constants keyIsEnabled, keyIsSystem, and keyLastUpdated.
* Use the method String on instance of Duration instead of fmt.Sprintf.
* Replace any usage of io/ioutil package with its replacement.
* Check for error from calling Environment.init and Zone.Add.
* Prefix all returned error on hostsBlock.update method.
* Add "lint" task as part of default target, build.

4 files changed, 45 insertions, 26 deletions

diff --git a/Makefile b/Makefile
index 5f6141f..eed784e 100644
--- a/Makefile
+++ b/Makefile
@@ -33,7 +33,7 @@ DIR_BIN=/usr/bin
 DIR_MAN=/usr/share/man
 DIR_RESCACHED=/usr/share/rescached
 
-build: test memfs_generate.go
+build: lint test memfs_generate.go
 	mkdir -p _bin/$(GOOS)_$(GOARCH)
 	CGO_ENABLED=$(CGO_ENABLED) GOOS=$(GOOS) GOARCH=$(GOARCH) \
 		go build $(DEBUG) -o _bin/$(GOOS)_$(GOARCH)/ ./cmd/...
@@ -52,7 +52,7 @@ test.prof:
 		-memprofile $(MEM_PROF) ./...
 
 lint:
-	-golangci-lint run --enable-all ./...
+	-golangci-lint run ./...
 
 memfs_generate.go: .FORCE
 	go run ./cmd/rescached embed
diff --git a/environment.go b/environment.go
index b8f2729..a4d7923 100644
--- a/environment.go
+++ b/environment.go
@@ -36,9 +36,6 @@ const (
 	keyDohBehindProxy      = "doh.behind_proxy"
 	keyHostsBlock          = "hosts_block"
 	keyHTTPPort            = "http.port"
-	keyIsEnabled           = "is_enabled"
-	keyIsSystem            = "is_system"
-	keyLastUpdated         = "last_updated"
 	keyListen              = "listen"
 	keyParent              = "parent"
 	keyWUIListen           = "wui.listen"
@@ -90,7 +87,7 @@ func LoadEnvironment(fileConfig string) (env *Environment, err error) {
 	env.fileConfig = fileConfig
 
 	if len(fileConfig) == 0 {
-		env.init()
+		_ = env.init()
 		return env, nil
 	}
 
@@ -266,10 +263,8 @@ func (env *Environment) save(file string) (in *ini.Ini, err error) {
 	in.Set(sectionNameDNS, subNameServer, keyDohBehindProxy,
 		fmt.Sprintf("%t", env.ServerOptions.DoHBehindProxy))
 
-	in.Set(sectionNameDNS, subNameServer, keyCachePruneDelay,
-		fmt.Sprintf("%s", env.ServerOptions.PruneDelay))
-	in.Set(sectionNameDNS, subNameServer, keyCachePruneThreshold,
-		fmt.Sprintf("%s", env.ServerOptions.PruneThreshold))
+	in.Set(sectionNameDNS, subNameServer, keyCachePruneDelay, env.ServerOptions.PruneDelay.String())
+	in.Set(sectionNameDNS, subNameServer, keyCachePruneThreshold, env.ServerOptions.PruneThreshold.String())
 
 	return in, nil
 }
diff --git a/hosts_block.go b/hosts_block.go
index c80bc9a..4a829be 100644
--- a/hosts_block.go
+++ b/hosts_block.go
@@ -6,7 +6,7 @@ package rescached
 import (
 	"bytes"
 	"fmt"
-	"io/ioutil"
+	"io"
 	"log"
 	"net/http"
 	"os"
@@ -58,29 +58,37 @@ func (hb *hostsBlock) update() (err error) {
 		return nil
 	}
 
-	fmt.Printf("hostsBlock %s: updating ...\n", hb.Name)
+	var (
+		logp = "hostsBlock.update"
 
-	res, err := http.Get(hb.URL)
+		res      *http.Response
+		body     []byte
+		errClose error
+	)
+
+	fmt.Printf("%s %s: updating ...\n", logp, hb.Name)
+
+	res, err = http.Get(hb.URL)
 	if err != nil {
-		return fmt.Errorf("hostsBlock.update %q: %w", hb.Name, err)
+		return fmt.Errorf("%s %s: %w", logp, hb.Name, err)
 	}
 	defer func() {
-		err := res.Body.Close()
-		if err != nil {
-			log.Printf("hostsBlock.update %q: %s", hb.Name, err)
+		errClose = res.Body.Close()
+		if errClose != nil {
+			log.Printf("%s %q: %s", logp, hb.Name, err)
 		}
 	}()
 
-	body, err := ioutil.ReadAll(res.Body)
+	body, err = io.ReadAll(res.Body)
 	if err != nil {
-		return fmt.Errorf("hostsBlock.update %q: %w", hb.Name, err)
+		return fmt.Errorf("%s %q: %w", logp, hb.Name, err)
 	}
 
 	body = bytes.ReplaceAll(body, []byte("\r\n"), []byte("\n"))
 
-	err = ioutil.WriteFile(hb.file, body, 0644)
+	err = os.WriteFile(hb.file, body, 0644)
 	if err != nil {
-		return fmt.Errorf("hostsBlock.update %q: %w", hb.Name, err)
+		return fmt.Errorf("%s %q: %w", logp, hb.Name, err)
 	}
 
 	hb.initLastUpdated()
diff --git a/httpd.go b/httpd.go
index 7eacaa1..c698bf4 100644
--- a/httpd.go
+++ b/httpd.go
@@ -325,6 +325,7 @@ func (srv *Server) httpdAPIGetEnvironment(epr *libhttp.EndpointRequest) (resBody
 
 func (srv *Server) httpdAPIPostEnvironment(epr *libhttp.EndpointRequest) (resBody []byte, err error) {
 	var (
+		logp    = "httpdAPIPostEnvironment"
 		res     = libhttp.EndpointResponse{}
 		newOpts = new(Environment)
 	)
@@ -342,7 +343,12 @@ func (srv *Server) httpdAPIPostEnvironment(epr *libhttp.EndpointRequest) (resBod
 		return nil, &res
 	}
 
-	newOpts.init()
+	err = newOpts.init()
+	if err != nil {
+		res.Code = http.StatusInternalServerError
+		res.Message = fmt.Sprintf("%s: %s", logp, err)
+		return nil, &res
+	}
 
 	fmt.Printf("new options: %+v\n", newOpts)
 
@@ -474,17 +480,22 @@ func (srv *Server) hostsBlockEnable(hb *hostsBlock) (err error) {
 }
 
 func (srv *Server) hostsBlockDisable(hb *hostsBlock) (err error) {
-	var hfile *dns.HostsFile
+	var (
+		logp = "hostsBlockDisable"
+
+		hfile *dns.HostsFile
+	)
+
 	hfile = srv.env.HostsFiles[hb.Name]
 	if hfile == nil {
-		return fmt.Errorf("unknown hosts block: %q", hb.Name)
+		return fmt.Errorf("%s: unknown hosts block: %q", logp, hb.Name)
 	}
 
 	srv.dns.RemoveLocalCachesByNames(hfile.Names())
 
 	err = hb.hide()
 	if err != nil {
-		return err
+		return fmt.Errorf("%s: %w", logp, err)
 	}
 	delete(srv.env.HostsFiles, hb.Name)
 
@@ -872,7 +883,12 @@ func (srv *Server) apiZoneRRCreate(epr *libhttp.EndpointRequest) (resbody []byte
 	}
 
 	// Update the Zone file.
-	zoneFile.Add(rr)
+	err = zoneFile.Add(rr)
+	if err != nil {
+		res.Message = err.Error()
+		return nil, &res
+	}
+
 	err = zoneFile.Save()
 	if err != nil {
 		res.Message = err.Error()