使用golang根据位置解析字符串的好方法是什么？

I'm designing an simple application using go to read a few file formats representing customers file formats. My first idea is to read each file line and then parse it to an struct. So far so good, but i need to split each field based on it's index. For example:

line := "1003450020170804890000000022344"

Id starts on position 1 to position 4 = 1003 CustomerId is position 5 to 7 and all other fields related to that structure.

I would like to know if there's something more efficient to read a format and apply to this file line, i thought to create some struct for each field and have the start and end fields, but it sounds weird to me.

type Record struct {
Id       int
Date     time.Time
Value    float64
ClientId int32
}

type RecordId struct {
  Start  int
  Finish int
  Value  int
}

type ClientId struct {
  Start  int
  Finish int
  Value  int32
}

I don't know if i'm on the way, maybe there's something more elegant that will work better on this case.

var a, b int
n, err := fmt.Sscanf("1003450020170804890000000022344", "%4d%3d", &a, &b)
if err != nil {
   // ...
}

fmt.Println(a) // 1003
fmt.Println(b) // 450

Then you could create a structure with these.

A parse function is simple and probably sufficient, rather than declaring ancillary data structures.

Eg, something along the lines of:

func NewRecord(line string) (*Record, error) {

    if len(line) < 14 {
        return nil, fmt.Errorf("line is too short: %d", len(line))
    }

    return &Record{
        Id:   line[0:4],
        Name: line[4:14],
    }, nil
}