3P

06-functions-methods/44-side-effects-named-result-parameters/main.go

@@ -5,9 +5,9 @@ import (
 	"errors"
 )
 
-type locator struct{}
+type loc struct{}
 
-func (l locator) getCoordinates1(ctx context.Context, address string) (
+func (l loc) getCoordinates1(ctx context.Context, address string) (
 	lat, lng float32, err error) {
 	isValid := l.validateAddress(address)
 	if !isValid {
@@ -22,7 +22,7 @@ func (l locator) getCoordinates1(ctx context.Context, address string) (
 	return 0, 0, nil
 }
 
-func (l locator) getCoordinates2(ctx context.Context, address string) (
+func (l loc) getCoordinates2(ctx context.Context, address string) (
 	lat, lng float32, err error) {
 	isValid := l.validateAddress(address)
 	if !isValid {
@@ -37,6 +37,21 @@ func (l locator) getCoordinates2(ctx context.Context, address string) (
 	return 0, 0, nil
 }
 
-func (l locator) validateAddress(address string) bool {
+func (l loc) getCoordinates3(ctx context.Context, address string) (
+	lat, lng float32, err error) {
+	isValid := l.validateAddress(address)
+	if !isValid {
+		return 0, 0, errors.New("invalid address")
+	}
+
+	if err = ctx.Err(); err != nil {
+		return
+	}
+
+	// Get and return coordinates
+	return 0, 0, nil
+}
+
+func (l loc) validateAddress(address string) bool {
 	return true
 }

08-concurrency-foundations/58-races/races/main.go

@@ -68,13 +68,13 @@ func listing5() {
 
 	go func() {
 		mutex.Lock()
+		defer mutex.Unlock()
 		i = 1
-		mutex.Unlock()
 	}()
 
 	go func() {
 		mutex.Lock()
+		defer mutex.Unlock()
 		i = 2
-		mutex.Unlock()
 	}()
 }

08-concurrency-foundations/59-workload-type/main.go

@@ -40,11 +40,11 @@ func read2(r io.Reader) (int, error) {
 	wg.Add(n)
 	for i := 0; i < n; i++ {
 		go func() {
+			defer wg.Done()
 			for b := range ch {
 				v := task(b)
 				atomic.AddInt64(&count, int64(v))
 			}
-			wg.Done()
 		}()
 	}
 

09-concurrency-practice/68-string-formatting/main.go

@@ -1,11 +1,17 @@
 package main
 
 import (
-	"errors"
 	"fmt"
 	"sync"
 )
 
+func main() {
+	customer := Customer{}
+	_ = customer.UpdateAge1(-1)
+	_ = customer.UpdateAge2(-1)
+	_ = customer.UpdateAge3(-1)
+}
+
 type Customer struct {
 	mutex sync.RWMutex
 	id    string
@@ -17,7 +23,7 @@ func (c *Customer) UpdateAge1(age int) error {
 	defer c.mutex.Unlock()
 
 	if age < 0 {
-		return errors.New("age should be positive")
+		return fmt.Errorf("age should be positive for customer %v", c)
 	}
 
 	c.age = age
@@ -26,7 +32,7 @@ func (c *Customer) UpdateAge1(age int) error {
 
 func (c *Customer) UpdateAge2(age int) error {
 	if age < 0 {
-		return errors.New("age should be positive")
+		return fmt.Errorf("age should be positive for customer %v", c)
 	}
 
 	c.mutex.Lock()
@@ -36,6 +42,18 @@ func (c *Customer) UpdateAge2(age int) error {
 	return nil
 }
 
+func (c *Customer) UpdateAge3(age int) error {
+	c.mutex.Lock()
+	defer c.mutex.Unlock()
+
+	if age < 0 {
+		return fmt.Errorf("age should be positive for customer id %s", c.id)
+	}
+
+	c.age = age
+	return nil
+}
+
 func (c *Customer) String() string {
 	c.mutex.RLock()
 	defer c.mutex.RUnlock()

09-concurrency-practice/70-mutex-slices-maps/main.go

@@ -1,6 +1,20 @@
 package main
 
-import "sync"
+import (
+	"fmt"
+	"sync"
+)
+
+func main() {
+	c := Cache{
+		balances: make(map[string]float64),
+	}
+	c.AddBalance("1", 1.0)
+	c.AddBalance("2", 3.0)
+	fmt.Println(c.AverageBalance1())
+	fmt.Println(c.AverageBalance2())
+	fmt.Println(c.AverageBalance3())
+}
 
 type Cache struct {
 	mu       sync.Mutex
@@ -48,5 +62,5 @@ func (c *Cache) AverageBalance3() float64 {
 	for _, balance := range m {
 		sum += balance
 	}
-	return sum / float64(len(c.balances))
+	return sum / float64(len(m))
 }

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

@@ -1,13 +1,21 @@
 package main
 
-import "time"
+import (
+	"fmt"
+	"time"
+)
+
+func main() {
+	listing1()
+	//listing2()
+}
 
 func listing1() {
 	ticker := time.NewTicker(1000)
 	for {
 		select {
 		case <-ticker.C:
-			// Do something
+			fmt.Println("tick")
 		}
 	}
 }
@@ -17,7 +25,7 @@ func listing2() {
 	for {
 		select {
 		case <-ticker.C:
-			// Do something
+			fmt.Println("tick")
 		}
 	}
 }

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

@@ -13,6 +13,9 @@ func main() {
 	if err := listing2(); err != nil {
 		panic(err)
 	}
+	if err := listing3(); err != nil {
+		panic(err)
+	}
 }
 
 type Event1 struct {
@@ -54,3 +57,35 @@ func listing2() error {
 	fmt.Println(string(b))
 	return nil
 }
+
+type Event3 struct {
+	ID int
+	time.Time
+}
+
+func (e Event3) MarshalJSON() ([]byte, error) {
+	return json.Marshal(
+		struct {
+			ID   int
+			Time time.Time
+		}{
+			ID:   e.ID,
+			Time: e.Time,
+		},
+	)
+}
+
+func listing3() error {
+	event := Event3{
+		ID:   1234,
+		Time: time.Now(),
+	}
+
+	b, err := json.Marshal(event)
+	if err != nil {
+		return err
+	}
+
+	fmt.Println(string(b))
+	return nil
+}

11-testing/82-categorizing-tests/build-tags/db_test.go

@@ -1,8 +1,10 @@
+//go:build integration
 // +build integration
 
 package db
 
 import (
+	"os"
 	"testing"
 )