Resolved #3

README.md

@@ -23,6 +23,7 @@ $ go get -u github.com/shinYeongHyeon/go-times
   - [GetDateOfFirstFridayOfMonth](#getDateOfFirstFridayOfMonth)
   - [GetDateOfFirstSaturdayOfMonth](#getDateOfFirstSaturdayOfMonth)
   - [GetDateOfFirstSundayOfMonth](#getDateOfFirstSundayOfMonth)
+  - [GetFirstWorkingTimeOfMonth](#getFirstWorkingTimeOfMonth)
   - [GetNthWeekOfMonth](#getNthWeekOfMonth)
   - [GetLastTimeOfMonth](#getLastTimeOfMonth)
 
@@ -74,6 +75,12 @@ This will get date of first sunday of month
 func GetDateOfFirstSundayOfMonth(t time.Time) int
 ```
 
+#### GetFirstWorkingTimeOfMonth
+This will get First Working TimeObject of request year, month.
+```go
+func GetFirstWorkingTimeOfMonth(year, month int) time.Time
+```
+
 #### GetNthWeekOfMonth
 This will get `n`th Week of Month  
 (Regard the start of the week as Sunday)

constant.go

@@ -14,17 +14,17 @@ var DaysMap = map[time.Weekday]int{
 }
 
 // MonthMap is dependent for time package
-var MonthMap = map[time.Month]int{
-	time.January:   1,
-	time.February:  2,
-	time.March:     3,
-	time.April:     4,
-	time.May:       5,
-	time.June:      6,
-	time.July:      7,
-	time.August:    8,
-	time.September: 9,
-	time.October:   10,
-	time.November:  11,
-	time.December:  12,
+var MonthMapByInt = map[int]time.Month{
+	1: time.January,
+	2: time.February,
+	3: time.March,
+	4: time.April,
+	5: time.May,
+	6: time.June,
+	7: time.July,
+	8: time.August,
+	9: time.September,
+	10: time.October,
+	11: time.November,
+	12: time.December,
 }

times.go

@@ -94,6 +94,19 @@ func GetLastTimeOfMonth(t time.Time) time.Time {
 	return getFirstTimeOfMonth(t).AddDate(0, 1, -1)
 }
 
+// GetFirstWorkingTimeOfMonth : get First Working TimeObject Of Request Month
+func GetFirstWorkingTimeOfMonth(year, month int) time.Time {
+	firstDateOfMonth := time.Date(year, MonthMapByInt[month], 1, 0, 0, 0, 0, time.UTC)
+
+	if firstDateOfMonth.Weekday() == 0 {
+		return firstDateOfMonth.AddDate(0, 0, 1)
+	} else if firstDateOfMonth.Weekday() == 6 {
+		return firstDateOfMonth.AddDate(0, 0, 2)
+	}
+
+	return firstDateOfMonth
+}
+
 // getDayOfFirstDateOfMonth : get day of first date
 func getDayOfFirstDateOfMonth(t time.Time) int {
 	return DaysMap[(getFirstTimeOfMonth(t)).Weekday()]

times_test.go

@@ -7,10 +7,11 @@ import (
 
 var startedMondayMonth time.Time = time.Date(2021, 2, 3, 0, 0, 0, 0, time.UTC)
 var startedSaturdayMonth time.Time = time.Date(2021, 5, 3, 0, 0, 0, 0, time.UTC)
-var startedSundayMonth time.Time = time.Date(2021, 8, 3, 0, 0, 0, 0, time.UTC)
+var startedSundayMonth time.Time = time.Date(2021, 8, 2, 0, 0, 0, 0, time.UTC)
 var lastTimeOf202108 time.Time = time.Date(2021, 8, 31, 0, 0, 0, 0, time.UTC)
 var lastTimeOf202002 time.Time = time.Date(2020, 2, 29, 0, 0, 0, 0, time.UTC)
 var timeOf20200206 time.Time = time.Date(2020, 2, 6, 0, 0, 0, 0, time.UTC)
+var timeOf20210201 time.Time = time.Date(2021, 6, 1, 0, 0, 0, 0, time.UTC)
 
 func TestGetDateOfFirstMondayOfMonth(t *testing.T) {
 	want := 1
@@ -113,4 +114,21 @@ func TestGetLastTimeOfMonth(t *testing.T) {
 	if got := GetLastTimeOfMonth(timeOf20200206); got != want {
 		t.Errorf("GetLastTimeOfMonth() = %v, want %v", got, want)
 	}
+}
+
+func TestGetFirstWorkingTimeOfMonth(t *testing.T) {
+	want := startedSaturdayMonth
+	if got := GetFirstWorkingTimeOfMonth(2021, 5); got != want {
+		t.Errorf("GetLastTimeOfMonth() = %v, want %v", got, want)
+	}
+
+	want = timeOf20210201
+	if got := GetFirstWorkingTimeOfMonth(2021, 6); got != want {
+		t.Errorf("GetLastTimeOfMonth() = %v, want %v", got, want)
+	}
+
+	want = startedSundayMonth
+	if got := GetFirstWorkingTimeOfMonth(2021, 8); got != want {
+		t.Errorf("GetLastTimeOfMonth() = %v, want %v", got, want)
+	}
 }