workers/workers'

Workers' with an apostrophe after the final s of workers. This is the plural possessive.

When the plural of the noun ends in s, add an apostophe only, e.g. the kittens' toys, the workers' plight.

When the plural of the noun does not end in s, add the possessive apostrophe and an s, e.g. the men's room, the women's room.

When the singular and plural of the noun both end in an s, the possessives for both are identical and are formed by adding an apostrophe only, e.g. the species' status was changed to endangered. In these cases, it may be necessary to reword the sentence to avoid ambiguity and to clarify whether you are referring to a singular or plural noun, e.g. the status of the two species was changed to endangered; the status of the species was changed to endangered.

Thanks, contrex, for the detailed explanation.

So it's wrong to use workers without apostrophe.

Correct: the worker's plight (the plight of one worker)

Correct: the workers' plight (the shared plight of a number of workers greater than one)

Incorrect: the workers plight, however...

Correct: the plight of the workers

Thanks again, contrex.

Just a final two notes.

The apostrophe alone only works as a possessive if the last letter of the noun is s or z. The noun can be either a plural, (workers), or singular, (James).

So:
It is a violation of the workers' rights.
But: It's the jury's decision.

That is James' video.
But: That is Ann's video.

The glitz' shine was dimming.
But: The sheen's intensity was dimming.