log-level based logging added to ease debugging persistence on K8s

* new slog in stdlib is utilized for that and replaces 'log' pkg
* configuration pkg is used validate and now set/define/refer
  log level values
* the 'error' level call is not fatal, thus os.Exit is called
  instead

configuration/config.go

@@ -4,6 +4,7 @@ import (
     "errors"
     "fmt"
     "os"
+    "log/slog"
     "unicode"
     fp "path/filepath"
 
@@ -58,14 +59,8 @@ func New() ( *Config, error ){
 
     if cfg.Environment == "development" { cfg.LogLevel = "debug" }
 
-    possibleLogLevels := map[ string ] bool {
-        "error":    true,
-        "debug":    true,
-    }
-    if _, ok := possibleLogLevels[ cfg.LogLevel ]; !ok {
-        return nil, errors.New(
-            fmt.Sprintf( "Invalid log level: %s", cfg.LogLevel ),
-        )
+    if _, err := cfg.GetLogLevel(); err != nil {
+        return nil, err
     }
 
     if len( cfg.DatabaseHost ) >= 1 && len( cfg.DatabasePassword ) >= 2 {
@@ -106,3 +101,19 @@ func New() ( *Config, error ){
 
     return &cfg, nil
 }
+
+
+func ( cfg *Config ) GetLogLevel() ( slog.Level, error ){
+    possibleLogLevels := map[ string ] slog.Level {
+        "error":    slog.LevelError,
+        "debug":    slog.LevelDebug,
+    }
+    level, ok := possibleLogLevels[ cfg.LogLevel ]
+    if !ok {
+        return slog.LevelError, errors.New(
+            fmt.Sprintf( "Invalid log level: %s", cfg.LogLevel ),
+        )
+    }else{
+        return level, nil
+    }
+}
\ No newline at end of file

main.go

@@ -4,6 +4,7 @@ import (
     "context"
     "fmt"
     "log"
+    "log/slog"
     "os"
     "os/signal"
     "syscall"
@@ -20,9 +21,22 @@ import (
 func main() {
     config, err := configuration.New()
     if err != nil {
-        log.Fatalf( "HTTP server failed to start: %v", err )
+        slog.Error( fmt.Sprintf( "HTTP server failed to start: %v", err ) )
+        os.Exit( 1 )
     }
 
+    level, _ := config.GetLogLevel()
+    slog.SetDefault(
+        slog.New(
+            slog.NewTextHandler(
+                os.Stdout,
+                &slog.HandlerOptions{
+                    Level: level,
+                },
+            ),
+        ),
+    )
+
     server := fiber.New( fiber.Config{
         AppName: "webservice",
         DisableStartupMessage: config.Environment != "development",
@@ -40,13 +54,15 @@ func main() {
 
     err = routing.SetRoutes( server, config, store, &isHealthy )
     if err != nil {
-        log.Fatalf( "HTTP server failed to start: %v", err )
+        slog.Error( fmt.Sprintf( "HTTP server failed to start: %v", err ) )
+        os.Exit( 1 )
     }
 
     go func(){
         err := server.Listen( fmt.Sprintf( "%s:%d", config.Host, config.Port ) )
         if err != nil {
-            log.Fatalf( "HTTP server failed to start: %v", err )
+            slog.Error( fmt.Sprintf( "HTTP server failed to start: %v", err ) )
+            os.Exit( 1 )
         }
     }()
 

routing/routes.go

@@ -7,7 +7,7 @@ import (
     "strings"
     "net/http"
     "html/template"
-    "log"
+    log "log/slog"
     "bytes"
     "mime"
 
@@ -32,11 +32,13 @@ func SetRoutes( router *f.App, config *configuration.Config, store state.Store,
 
     if config.LogLevel == "debug" {
         router.All( "*", func( c *f.Ctx ) error {
-            log.Printf( "%s %s  mime:%s  agent:%s",
-                c.Method(),
-                c.Path(),
-                c.Get( f.HeaderContentType, c.Get( f.HeaderAccept, "" ) ),
-                c.Get( f.HeaderUserAgent ),
+            log.Debug(
+                fmt.Sprintf( "%s %s  mime:%s  agent:%s",
+                    c.Method(),
+                    c.Path(),
+                    c.Get( f.HeaderContentType, c.Get( f.HeaderAccept, "" ) ),
+                    c.Get( f.HeaderUserAgent ),
+                ),
             )
             return c.Next()
         })
@@ -106,6 +108,7 @@ func SetRoutes( router *f.App, config *configuration.Config, store state.Store,
         } else {
             names, err := store.List()
             if err != nil {
+                log.Debug( err.Error() )
                 return c.SendStatus( http.StatusInternalServerError )
             }
 
@@ -135,6 +138,7 @@ func SetRoutes( router *f.App, config *configuration.Config, store state.Store,
         for _, envVar := range os.Environ() {
             _, err := c.WriteString( fmt.Sprintln( envVar ) )
             if err != nil {
+                log.Debug( err.Error() )
                 c.Status( http.StatusInternalServerError )
                 return err
             }
@@ -152,6 +156,7 @@ func SetRoutes( router *f.App, config *configuration.Config, store state.Store,
         name := strings.Clone( c.Params( "name" ) )
         existingItem, err := store.Fetch( name )
         if err != nil {
+            log.Debug( err.Error() )
             return c.SendStatus( http.StatusInternalServerError )
         }
 
@@ -167,6 +172,7 @@ func SetRoutes( router *f.App, config *configuration.Config, store state.Store,
     statePathGroup.Get( "/:name", func( c *f.Ctx ) error {
         existingItem, err := store.Fetch( c.Params( "name" ) )
         if err != nil {
+            log.Debug( err.Error() )
             c.Status( http.StatusInternalServerError )
             return c.Send( nil )
         }
@@ -193,6 +199,7 @@ func SetRoutes( router *f.App, config *configuration.Config, store state.Store,
         name := strings.Clone( c.Params( "name" ) )
         existingItem, err := store.Fetch( name )
         if err != nil {
+            log.Debug( err.Error() )
             c.Status( http.StatusInternalServerError )
             return c.Send( nil )
         }
@@ -216,6 +223,7 @@ func SetRoutes( router *f.App, config *configuration.Config, store state.Store,
         )
 
         if err = store.Add( newItem ); err != nil {
+            log.Debug( err.Error() )
             c.Status( http.StatusInternalServerError )
             return c.Send( nil )
         }
@@ -229,6 +237,7 @@ func SetRoutes( router *f.App, config *configuration.Config, store state.Store,
         name := strings.Clone( c.Params( "name" ) )
         existingItem, err := store.Fetch( name )
         if err != nil {
+            log.Debug( err.Error() )
             return c.SendStatus( http.StatusInternalServerError )
         }
 
@@ -237,6 +246,7 @@ func SetRoutes( router *f.App, config *configuration.Config, store state.Store,
         }
 
         if err = store.Remove( name ); err != nil {
+            log.Debug( err.Error() )
             return c.SendStatus( http.StatusInternalServerError )
         }
 
@@ -248,6 +258,7 @@ func SetRoutes( router *f.App, config *configuration.Config, store state.Store,
         name := strings.Clone( c.Params( "name" ) )
         existingItem, err := store.Fetch( name )
         if err != nil {
+            log.Debug( err.Error() )
             return c.SendStatus( http.StatusInternalServerError )
         }
 
@@ -269,6 +280,7 @@ func SetRoutes( router *f.App, config *configuration.Config, store state.Store,
     router.Get( "/states", func( c *f.Ctx ) error {
         names, err := store.List()
         if err != nil {
+            log.Debug( err.Error() )
             return c.SendStatus( http.StatusInternalServerError )
         }