add the struct package english docs (#82)

docs/structs/struct.md

@@ -1,2 +1,213 @@
 # Structs
 
+Struct is abstract struct for provide several high level functions
+
+<div STYLE="page-break-after: always;"></div>
+
+## Source:
+
+-   [https://github.com/duke-git/lancet/blob/main/structs/struct.go](https://github.com/duke-git/lancet/blob/main/structs/struct.go)
+
+<div STYLE="page-break-after: always;"></div>
+
+## Usage:
+
+```go
+import (
+    "github.com/duke-git/lancet/v2/structs"
+)
+```
+
+<div STYLE="page-break-after: always;"></div>
+
+## Index:
+-   [New](#New)
+-   [ToMap](#ToMap)
+-   [Fields](#Fields)
+-   [Field](#Field)
+-   [IsStruct](#IsStruct)
+
+<div STYLE="page-break-after: always;"></div>
+
+## Documentation:
+
+### <span id="New">New</span>
+
+<p>The constructor function of the `Struct` </p>
+
+<b>Signature:</b>
+
+```go
+func New(value any, tagName ...string) *Struct
+```
+
+<b>Example:</b>
+
+```go
+package main
+
+import (
+	"github.com/duke-git/lancet/v2/structs"
+)
+
+func main() {
+	type People struct {
+		Name string `json:"name"`
+	}
+	p1 := &People{Name: "11"}
+	s := structs.New(p1)
+	// to do something
+}
+```
+
+### <span id="ToMap">ToMap</span>
+
+<p>convert a valid struct to a map</p>
+
+<b>Signature:</b>
+
+```go
+func (s *Struct) ToMap() (map[string]any, error)
+```
+
+> In addition, provided a convenient static function ToMap
+
+```go
+func ToMap(v any) (map[string]any, error)
+```
+
+<b>Example:</b>
+
+```go
+package main
+
+import (
+	"fmt"
+	"github.com/duke-git/lancet/v2/structs"
+)
+
+func main() {
+	type People struct {
+		Name string `json:"name"`
+	}
+	p1 := &People{Name: "11"}
+	// use constructor function
+	s1 := structs.New(p1)
+	m1, _ := s1.ToMap()
+
+	fmt.Println(m1)
+	
+	// use static function
+	m2, _ := structs.ToMap(p1)
+	
+	fmt.Println(m2)
+	
+	// Output: 
+	// map[name:11]
+	// map[name:11]
+}
+```
+
+### <span id="Fields">Fields</span>
+
+<p>Get all fields of a given struct, that the fields are abstract struct field</p>
+
+<b>Signature:</b>
+
+```go
+func (s *Struct) Fields() []*Field
+```
+
+<b>Example:</b>
+
+```go
+package main
+
+import (
+	"fmt"
+	"github.com/duke-git/lancet/v2/structs"
+)
+
+func main() {
+	type People struct {
+		Name string `json:"name"`
+	}
+	p1 := &People{Name: "11"}
+	s := structs.New(p1)
+	fields := s.Fields()
+
+	fmt.Println(len(fields))
+	
+	// Output: 
+	// 1
+}
+```
+
+### <span id="Field">Field</span>
+
+<p>Get an abstract field of a struct by given field name </p>
+
+<b>Signature:</b>
+
+```go
+func (s *Struct) Field(name string) *Field
+```
+
+<b>Example:</b>
+
+```go
+package main
+
+import (
+	"fmt"
+	"github.com/duke-git/lancet/v2/structs"
+)
+
+func main() {
+	type People struct {
+		Name string `json:"name"`
+	}
+	p1 := &People{Name: "11"}
+	s := structs.New(p1)
+	f := s.Field("Name")
+
+	fmt.Println(f.Value())
+	
+	// Output: 
+	// 11
+}
+```
+
+### <span id="IsStruct">IsStruct</span>
+
+<p>Check if the struct is valid</p>
+
+<b>Signature:</b>
+
+```go
+func (s *Struct) IsStruct() bool
+```
+
+<b>Example:</b>
+
+```go
+package main
+
+import (
+	"fmt"
+	"github.com/duke-git/lancet/v2/structs"
+)
+
+func main() {
+	type People struct {
+		Name string `json:"name"`
+	}
+	p1 := &People{Name: "11"}
+	s := structs.New(p1)
+
+	fmt.Println(s.IsStruct())
+	
+	// Output: 
+	// true
+}
+```