Why does `reflect.Value.FieldByName` panic when called on a pointer value?

Reflect.Value.FieldByName Causing Panic

The .FieldByName method of a reflected value generates a panic when called on a pointer Value. The error message, "reflect: call of reflect.Value.FieldByName on ptr Value," is thrown when the provided value is a pointer to a struct rather than the struct itself.

In the code provided, the line "s := reflect.ValueOf(&value).Elem()" creates a pointer to the value struct and then dereferences it using Elem(), which is unnecessary. Instead, to access and modify the struct's fields, use "s := reflect.ValueOf(value).Elem()".

The following corrected code snippet eliminates the panic:

s := reflect.ValueOf(value).Elem()
metric := s.FieldByName(subval.Metric).Interface()
fmt.Println(metric)

By directly reflecting on the struct's value instead of creating an unnecessary pointer, you can access and manipulate its fields correctly without encountering a panic.

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