fixed code quality issues using DeepSource

* Combine multiple `append`s into a single call

* Remove unnecessary use of slice

* Replace `strings.Index` with `strings.Contains`

* Added .deepsource.toml config file for DeepSource integration

.deepsource.toml

@@ -0,0 +1,17 @@
+version = 1
+
+test_patterns = ["**/*_test.go"]
+
+exclude_patterns = [
+    "_examples/**",
+    "_benchmarks/**",
+    ".github/**"
+]
+
+[[analyzers]]
+name = "go"
+enabled = true
+
+  [analyzers.meta]
+  import_paths = ["github.com/kataras/iris"]
+

context/accept_header.go

@@ -194,8 +194,8 @@ func init() {
 		var t octetType
 		isCtl := c <= 31 || c == 127
 		isChar := 0 <= c && c <= 127
-		isSeparator := strings.IndexRune(" \t\"(),/:;<=>?@[]\\{}", rune(c)) >= 0
+		isSeparator := strings.ContainsRune(" \t\"(),/:;<=>?@[]\\{}", rune(c))
-		if strings.IndexRune(" \t\r\n", rune(c)) >= 0 {
+		if strings.ContainsRune(" \t\r\n", rune(c)) {
 			t |= isSpace
 		}
 		if isChar && !isCtl && !isSeparator {

core/errgroup/errgroup.go

@@ -210,7 +210,7 @@ func (g *Group) Error() (s string) {
 }
 
 func (g *Group) getAllErrors() []error {
-	list := g.Errors[:]
+	list := g.Errors
 
 	if len(g.children) > 0 {
 		// return with order of definition.

i18n/internal/var.go

@@ -174,8 +174,7 @@ func getCases(loc *Locale, src map[string]interface{}) []interface{} {
 	cases := make([]interface{}, 0, len(pluralCases)*2)
 	for _, pluralCase := range pluralCases {
 		// fmt.Printf("%s=%v\n", pluralCase.Form, pluralCase.Value)
-		cases = append(cases, pluralCase.Form.String())
+		cases = append(cases, pluralCase.Form.String(), pluralCase.Value)
-		cases = append(cases, pluralCase.Value)
 	}
 
 	return cases