We can use 'shall' for the future (instead of will), but only in the first person, after 'I' or 'we'.
'I will be / I shall be on holiday in August.'
'We will know/We shall know the results soon.'
But NOT Everyone shall know the results soon.
I will and I shall have the same meaning here, but shall is a little formal. Both I will and I shall can be shortened to I'll, which is pronounced /ail/.
I'll be on holiday in August. (= I will OR I shall)
Shall has other meanings. We can use it in offers and suggestions:
Offer: Shall I pack up your shopping for you? ~ Oh, thank you.
Suggestion: Shall we all go out together? ~ Good idea.
Americans do not normally use shall for the future: 'I will be here tomorrow.'
The British use will for the future, but they can also use 'shall' in the first person:
I will/I shall be here tomorrow.
We will/We shall contact you.