Go 言語における無効日付(2月31日など)の扱い ref: http://qiita.com/spiegel-im-spiegel/items/42d115471cf2b5a80437

file0.go

package main

import (
    "fmt"
    "time"
)

func main() {
    tm := time.Date(2017, 1, 31, 0, 0, 0, 0, time.UTC)
    for i := 0; i < 6; i++ {
        fmt.Println(tm.Format("2006-01-02"))
        tm = tm.AddDate(0, 1, 0)
    }
}

file1.txt

2017-01-31
2017-03-03
2017-04-03
2017-05-03
2017-06-03
2017-07-03

file2.go

package main

import (
    "fmt"
    "time"
)

func main() {
    tm := time.Date(2017, 1, 31, 0, 0, 0, 0, time.UTC)
    for i := 0; i < 6; i++ {
        fmt.Println(tm.AddDate(0, i, 0).Format("2006-01-02"))
    }
}

file3.txt

2017-01-31
2017-03-03
2017-03-31
2017-05-01
2017-05-31
2017-07-01

file4.go

package main

import (
    "fmt"
    "time"
)

func main() {
    tm := time.Date(2017, 1, 31, 0, 0, 0, 0, time.UTC)
    for i := 0; i < 6; i++ {
        fmt.Println(tm.Format("2006-01-02"))
        tm = time.Date(tm.Year(), tm.Month()+2, 0, 0, 0, 0, 0, time.UTC)
    }
}

file5.txt

2017-01-31
2017-02-28
2017-03-31
2017-04-30
2017-05-31
2017-06-30

file6.go

tm := time.Date(2016, 1, 31, 0, 0, 0, 0, time.UTC)

file7.txt

2016-01-31
2016-02-29
2016-03-31
2016-04-30
2016-05-31
2016-06-30