try this :
package main
import (
"fmt"
"math/rand"
)

func main() {
target := rand.Intn(100) + 1
fmt.Println(target)
}
or this
package main
import (
"fmt"
"math/rand"
)

func main() {
target := rand.Intn(100)
fmt.Println(target + 1)
}

again you're not adding one in either case , while i suggested to only add it in one of the lines .

you don't need to do this twice "target := rand.Intn(100) + 1
fmt.Println(target + 1) " your basicly prints target +2 .
hope this hint helps

fmt.Println(target + 1) .... this edit worked