Parse the copybook via the lexer:

lexer := getLexer("resources/float.copybook")
fileStruct := parser.ParseLexData(lexer)    

Read the ebcdic bytes in:

readBytes, len := getBytes("resources/float.ebcdic")

Parse the binary data into fields:

parser.ParseBinaryData(&fileStruct, readBytes[0:len])

Print the field:

field, err := fileStruct.Field(fieldLabel)
	if err != nil {
		panic(err)
	}
	log.Printf("Type: %T", field.Data)
	switch field.Data.(type) {
	case int32:
		fmt.Printf("Data by field %s pull: %d\n", fieldLabel, field.Data)
	case int:
		fmt.Printf("Data by field %s pull: %d\n", fieldLabel, field.Data)
	case string:
		fmt.Printf("Data by field %s pull: %s\n", fieldLabel, field.Data)
	case float32:
		fmt.Printf("Data by field %s pull: %v\n", fieldLabel, field.Data)
	case decimal.Decimal:
		fmt.Printf("Data by field %s pull: %v\n", fieldLabel, field.Data)
		fmt.Printf("Raw Data: %08b\n", field.GetRawData())
	case []uint8:
		fmt.Printf("Data by field %s pull: %v\n", fieldLabel, field.Data)
		fmt.Printf("Raw Data: %08b\n", field.GetRawData())
	case []int8:
		fmt.Printf("Data by field %s pull: %v\n", fieldLabel, field.Data)
		fmt.Printf("Raw Data: %08b\n", field.GetRawData())
	default:
		fmt.Printf("Unsupported type in printField: %T, data: %08b", field.Data, field.GetRawData())
	}

Update the a field with new data:

err = field.SetData(float32(1.123e+19))
if err != nil {
	panic(err)
}

Get the modified data stream:

updatedBytes := parser.GetBinaryData(&fileStruct)
fmt.Printf("Modified Data: %08b", updatedBytes)

Copybook Definitions Supported:

• Signed Binary PIC S9(#) COMP, PIC S9 COMP
• Unsiged Binary PIC 9(#) COMP, PIC 9 COMP
• Float4 PIC S9(#)V9(#) COMP-1, PIC S9(#)V9(#) COMP-2
• Alpha Character PIC A(#)
• Any Character PIC X(#)
• Decimal PIC S9(#)V9(#) COMP-3

Unsupported Definitions:

• Float8
• Didplay Numeric

Made with lots of help from: https://techjogging.com/cobol-data-types.html