A fixed-width file use a fixed column width for each column (though not all columns necessarily have the same width) and pads the remaining space on the left or on the right, usually with spaces:
287540 Smith Jones Accountant $55,000
204878 Ross Betsy Senior Accountant $66,000
208417 Arthur Wilbur CEO $123,000
Parsing a fixed-width file can be difficult. Either, the user has to know the column widths in advance and pass that to a parsing method, or the method has to infer the widths of the columns.
This package Go propose automated infer the columns.
github.com/davidburil/fixedwidth-example
Project inspired by blog post at dev.to