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Author: teivah

Diff for: 10-standard-lib/75-wrong-time-duration/main.go

@@ -0,0 +1,23 @@
+package main
+
+import "time"
+
+func listing1() {
+	ticker := time.NewTicker(1000)
+	for {
+		select {
+		case <-ticker.C:
+			// Do something
+		}
+	}
+}
+
+func listing2() {
+	ticker := time.NewTicker(time.Microsecond)
+	for {
+		select {
+		case <-ticker.C:
+			// Do something
+		}
+	}
+}

Diff for: 10-standard-lib/76-time-after/main.go

@@ -0,0 +1,51 @@
+package main
+
+import (
+	"context"
+	"log"
+	"time"
+)
+
+func consumer1(ch <-chan Event) {
+	for {
+		select {
+		case event := <-ch:
+			handle(event)
+		case <-time.After(time.Hour):
+			log.Println("warning: no messages received")
+		}
+	}
+}
+
+func consumer2(ch <-chan Event) {
+	for {
+		ctx, cancel := context.WithTimeout(context.Background(), time.Hour)
+		select {
+		case event := <-ch:
+			cancel()
+			handle(event)
+		case <-ctx.Done():
+			log.Println("warning: no messages received")
+		}
+	}
+}
+
+func consumer3(ch <-chan Event) {
+	timerDuration := 1 * time.Hour
+	timer := time.NewTimer(timerDuration)
+
+	for {
+		timer.Reset(timerDuration)
+		select {
+		case event := <-ch:
+			handle(event)
+		case <-timer.C:
+			log.Println("warning: no messages received")
+		}
+	}
+}
+
+type Event struct{}
+
+func handle(Event) {
+}

Diff for: 10-standard-lib/77-json-handling/map-any/main.go

@@ -0,0 +1,17 @@
+package main
+
+import "encoding/json"
+
+func listing1() error {
+	b := getMessage()
+	var m map[string]any
+	err := json.Unmarshal(b, &m)
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+func getMessage() []byte {
+	return nil
+}

Diff for: 10-standard-lib/77-json-handling/monotonic-clock/main.go

@@ -0,0 +1,53 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"time"
+)
+
+type Event struct {
+	Time time.Time
+}
+
+func listing1() error {
+	t := time.Now()
+	event1 := Event{
+		Time: t,
+	}
+
+	b, err := json.Marshal(event1)
+	if err != nil {
+		return err
+	}
+
+	var event2 Event
+	err = json.Unmarshal(b, &event2)
+	if err != nil {
+		return err
+	}
+
+	fmt.Println(event1 == event2)
+	return nil
+}
+
+func listing2() error {
+	t := time.Now()
+	event1 := Event{
+		Time: t.Truncate(0),
+	}
+
+	b, err := json.Marshal(event1)
+	if err != nil {
+		return err
+	}
+
+	var event2 Event
+	err = json.Unmarshal(b, &event2)
+	if err != nil {
+		return err
+	}
+
+	fmt.Println(event1 == event2)
+	return nil
+}

Diff for: 10-standard-lib/77-json-handling/type-embedding/main.go

@@ -0,0 +1,56 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"time"
+)
+
+func main() {
+	if err := listing1(); err != nil {
+		panic(err)
+	}
+	if err := listing2(); err != nil {
+		panic(err)
+	}
+}
+
+type Event1 struct {
+	ID int
+	time.Time
+}
+
+func listing1() error {
+	event := Event1{
+		ID:   1234,
+		Time: time.Now(),
+	}
+
+	b, err := json.Marshal(event)
+	if err != nil {
+		return err
+	}
+
+	fmt.Println(string(b))
+	return nil
+}
+
+type Event2 struct {
+	ID   int
+	Time time.Time
+}
+
+func listing2() error {
+	event := Event2{
+		ID:   1234,
+		Time: time.Now(),
+	}
+
+	b, err := json.Marshal(event)
+	if err != nil {
+		return err
+	}
+
+	fmt.Println(string(b))
+	return nil
+}

Diff for: 10-standard-lib/78-sql/null-values/main.go

@@ -0,0 +1,66 @@
+package main
+
+import "database/sql"
+
+func listing1(db *sql.DB, id string) error {
+	rows, err := db.Query("SELECT DEP, AGE FROM EMP WHERE ID = ?", id)
+	if err != nil {
+		return err
+	}
+	// Defer closing rows
+
+	var (
+		department string
+		age        int
+	)
+	for rows.Next() {
+		err := rows.Scan(&department, &age)
+		if err != nil {
+			return err
+		}
+		// ...
+	}
+	return nil
+}
+
+func listing2(db *sql.DB, id string) error {
+	rows, err := db.Query("SELECT DEP, AGE FROM EMP WHERE ID = ?", id)
+	if err != nil {
+		return err
+	}
+	// Defer closing rows
+
+	var (
+		department *string
+		age        int
+	)
+	for rows.Next() {
+		err := rows.Scan(&department, &age)
+		if err != nil {
+			return err
+		}
+		// ...
+	}
+	return nil
+}
+
+func listing3(db *sql.DB, id string) error {
+	rows, err := db.Query("SELECT DEP, AGE FROM EMP WHERE ID = ?", id)
+	if err != nil {
+		return err
+	}
+	// Defer closing rows
+
+	var (
+		department sql.NullString
+		age        int
+	)
+	for rows.Next() {
+		err := rows.Scan(&department, &age)
+		if err != nil {
+			return err
+		}
+		// ...
+	}
+	return nil
+}

Diff for: 10-standard-lib/78-sql/prepared-statements/main.go

@@ -0,0 +1,16 @@
+package main
+
+import "database/sql"
+
+func listing1(db *sql.DB, id string) error {
+	stmt, err := db.Prepare("SELECT * FROM ORDER WHERE ID = ?")
+	if err != nil {
+		return err
+	}
+	rows, err := stmt.Query(id)
+	if err != nil {
+		return err
+	}
+	_ = rows
+	return nil
+}

Diff for: 10-standard-lib/78-sql/rows-iterations-errors/main.go

@@ -0,0 +1,68 @@
+package main
+
+import (
+	"context"
+	"database/sql"
+	"log"
+)
+
+func (c *conn) get1(ctx context.Context, id string) (string, int, error) {
+	rows, err := c.db.QueryContext(ctx,
+		"SELECT DEP, AGE FROM EMP WHERE ID = ?", id)
+	if err != nil {
+		return "", 0, err
+	}
+	defer func() {
+		err := rows.Close()
+		if err != nil {
+			log.Printf("failed to close rows: %v\n", err)
+		}
+	}()
+
+	var (
+		department string
+		age        int
+	)
+	for rows.Next() {
+		err := rows.Scan(&department, &age)
+		if err != nil {
+			return "", 0, err
+		}
+	}
+
+	return department, age, nil
+}
+
+func (c *conn) get2(ctx context.Context, id string) (string, int, error) {
+	rows, err := c.db.QueryContext(ctx,
+		"SELECT DEP, AGE FROM EMP WHERE ID = ?", id)
+	if err != nil {
+		return "", 0, err
+	}
+	defer func() {
+		err := rows.Close()
+		if err != nil {
+			log.Printf("failed to close rows: %v\n", err)
+		}
+	}()
+
+	var (
+		department string
+		age        int
+	)
+	for rows.Next() {
+		err := rows.Scan(&department, &age)
+		if err != nil {
+			return "", 0, err
+		}
+	}
+	if err := rows.Err(); err != nil {
+		return "", 0, err
+	}
+
+	return department, age, nil
+}
+
+type conn struct {
+	db *sql.DB
+}

Diff for: 10-standard-lib/78-sql/sql-open/main.go

@@ -0,0 +1,19 @@
+package main
+
+import "database/sql"
+
+var dsn = ""
+
+func listing1() error {
+	db, err := sql.Open("mysql", dsn)
+	if err != nil {
+		return err
+	}
+
+	if err := db.Ping(); err != nil {
+		return err
+	}
+
+	_ = db
+	return nil
+}